Aqueous coating composition comprising non-crosslinkable oligomer(s) and dispersed polymer(s)

ABSTRACT

An aqueous coating composition containing a non-crosslinkable water-dispersible oligomer(s); a dispersed polymer(s); water and optionally co-solvent wherein the composition has an open time of at least 20 minutes; a wet edge time of at least 10 minutes; a tack free time of ≦24 hours and an equilibrium viscosity of 5,000 Pa·s.

The present invention relates to certain compositions comprising anon-crosslinkable oligomer(s) which, inter alia, provide coatings havingimproved open and wet edge times as well as good tack-free times.

A general need when applying a decorative or protective coating to asubstrate, is to be able to repair irregularities in the still-wetcoating after some time has elapsed, for example by re-brushing over afreshly coated wet substrate, or by applying more of the coatingcomposition over a previously coated substrate either over the main areaof the coating or an edge of the coating or even blending a drop intothe coating without in each case vitiating the complete merging of anyboundaries in the vicinity of the repaired irregularity. Traditionallycompositions containing binder polymers dissolved in organic solventsare used and the organic solvents are employed to modify the dryingcharacteristics of the coated composition. For example, organic solventbased alkyds with an open time of 30 to 45 minutes are available in thedecorative “Do-it-Yourself” DIY market. However the disadvantage oforganic solvent based coatings is the toxic and flammable nature of suchsolvents and the pollution and odour caused on evaporation as well asthe relatively high cost of organic solvents.

Thus with the continuing concern about the use of organic solvent basedcoating compositions there has been a long felt need for an aqueouscoating composition with comparable properties to those achievable usingorganic solvent based compositions.

Unfortunately, aqueous polymer coating compositions currently known inthe art do not offer a combination of drying properties which would makethem fully comparable (or even superior to) solvent-based coatings, andin particular do not provide desirably long open and wet edge timestogether with desirably short tack-free times.

U.S. Pat. No. 6,303,189 discloses a method for increasing the open timeof an aqueous coating composition comprising mixing a film forming latexpolymer with a polyurethane polymer having a lower Tg than the latexpolymer.

U.S. Pat. No. 5,326,808 discloses a paint composition comprising apolymeric binder prepared by polymerising vinyl acetate monomer in thepresence of an oligomer. WO 00/24837 discloses an aqueous coatingcomposition comprising a blend of a polyurethane/acrylate hybrid and apolyurethane dispersion with open times up to and around 7 minutes and awet edge time of up to 4 minutes. U.S. Pat. No. 5,270,380 disclosesimproving open time through the interaction of a latex polymer and amodifying compound which becomes chemically bound to the latex polymer.

Thus, very commonly, aqueous-based polymer coating compositions employdispersed high molecular weight polymers as the binder materialsthereof. This results in, inter alia, a short wet edge time when thecoating composition is dried because the dispersed polymer particlestend to coalesce in the edge region of an applied coating very soonafter a wet coating has been applied (probably due to the maximumpacking fraction of the polymer particles having been reached) to form acontinuous film, and since the polymer of this film is of high viscositybecause of its highly molecular weight, the lapping (i.e. wet edge) timeof the composition is poor.

It has been shown by viscosity measurements taken during drying thatexisting alkyd emulsions have a high viscosity phase inversion peakduring drying. (Phase inversion is defined as the transition from abinder in a continuous water phase to water in a continuous binder phasewhich occurs during drying). The consequence is a difficulty inre-brushing which starts a few minutes after application of the coating.

It is known from the prior art that a longer wet edge or open time isachievable by using solution-type aqueous oligomers (EP 0136025 B1)which can be diluted with large amounts of organic solvent(s) in orderto create a low viscosity continuous phase during drying of the film andthese are generally unacceptably water-sensitive.

From the literature it is also known that open time is easily prolongedby using low solids contents in the aqueous polymer compositions, butthis generally results in the need to apply many layers of paint (forgood opacity). In addition, the wet edge time is generally onlymoderately influenced by reducing the solids content of an aqueouscoating composition with water.

Longer times for repairing irregularities can be achieved by employingaqueous polymer coating compositions in which the binder polymers havevery low viscosities. However, hitherto, a problem with using such lowviscosity polymer binders, is that the resultant coatings have a slowdrying rate, resulting in the coating remaining tacky for anunacceptably long time. A coating should preferably also drysufficiently quickly to avoid the adherence of dust and to ensure thatthe coating quickly becomes waterproof (in case of outdoorapplications), and, as discussed above, quickly becomes tack-free.

Indeed, the difficulty in developing aqueous polymer coatingcompositions having a desirable combination of drying properties whencoated onto a substrate has been particularly discussed in an interviewgiven by Professor Rob van der Linde (Professor of Coatings Technology,University of Technology, Eindhoven, NL) and Kees van der Kolk (SigmaCoatings) and reported in “Intermediair” Oct. 6, 1999, 35(23), pages27–29. In this interview, concerning environmentally friendly paints,there is described the problem of applying aqueous paints where even theprofessional painter has little enough time to correct anyirregularities when needed. This is contrasted (in the interview) withsolvent-based paints (e.g. alkyd paints) which are workable for a muchlonger time but have the disadvantage that the organic solvents, forminga major component of such compositions, are toxic and expensive. Theinterview also mentions that in the coming years, three universitieswill cooperate in a project to overcome the drying disadvantages ofaqueous paints. Thus this interview emphasises the current andcontinuing need and desirability for achieving aqueous polymer coatingscompositions having improved drying properties.

WO 02/32980, WO 02/33008, WO 02/33012 and WO 02/32982 all discloseaqueous coating composition comprising crosslinkable oligomers with opentimes of at least 20 minutes where the crosslinkability helps thebalance between a prolonged open time and a short tack free time.

The open time for a coating composition is, in brief, the period of timethat the main area (the bulk) of an applied aqueous coating remainsworkable after it has been applied to a substrate, in the sense thatduring this period re-brushing or application of more coating over themain area of a freshly coated wet substrate is possible without causingdefects such as brush marks in the final dried coating. (A more formaldefinition of open time is provided later in this specification).

The wet edge time for a coating composition is, in brief, the period oftime that the edge region of an applied aqueous coating remains workableafter it has been applied to a substrate, in the sense that during thisperiod re-brushing or application of more coating over the edge regionof a freshly coated wet substrate is possible without causing defectssuch as lap lines in the final dried coating. (A more formal definitionof wet edge time is provided later in this specification).

We have now invented aqueous coating compositions having a veryadvantageous combination of drying properties, particularly with regardto open time, wet edge time and tack-free time as discussed above, andwhich (surprisingly in view of the comments by van der Linde and van derKolk) avoid the drawbacks of the currently available compositions.

According to the present invention there is provided an aqueous coatingcomposition comprising:

-   -   a) 1 to 64 wt % of a non-crosslinkable water-dispersible        oligomer(s);    -   b) 4 to 76 wt % of a dispersed polymer(s);    -   c) 0 to 20 wt % of co-solvent;    -   d) 20 to 80 wt % of water;    -   where a)+b)+c)+d)=100%;    -   wherein the weight ratio of a):b) is in the range of from 8:92        to 80:20; and    -   wherein said composition when drying to form a coating has the        following properties:    -   i) an open time of at least 20 minutes;    -   ii) a wet edge time of at least 10 minutes;    -   iii) a tack-free time of ≦24 hours; and    -   iv) an equilibrium viscosity of ≦5,000 Pa·s, at any solids        content when drying in the range of from 20 to 55% by weight of        the composition, using any shear rate in the range of from 9±0.5        to 90±5 s⁻¹ and at 23±2° C.

The presence of the non-crosslinkable oligomer(s) appears to provide thedefined long open time and wet edge time, whilst the presence of thedispersed polymer(s) (e.g. in the form of a polymer latex) appears toassist in reducing the drying time of the composition.

Preferably the composition of the invention comprises a) 5 to 60 wt %,more preferably 8 to 40 wt % and most preferably 10 to 30 wt % of thenon-crosslinkable water-dispersible oligomer(s).

Preferably the composition of the invention comprises b) 10 to 65 wt %,more preferably 15 to 55 wt % and most preferably 15 to 45 wt % of thedispersed polymer(s).

Preferably the composition of the invention comprises d) 30 to 75 wt %,more preferably 40 to 70 wt % and most preferably 45 to 70 wt % ofwater.

Open time is more formally defined as the maximum length of time, usingthe test method and under the specified conditions described later, inwhich a brush carrying the aqueous composition of the invention can beapplied to the main area of a coating of the aqueous composition of theinvention after which the coating flows back so as to result in ahomogenous film layer.

Preferably the open time is at least 25 minutes, more preferably atleast 30 minutes and most preferably at least 35 minutes.

Wet edge time is more formally defined as the maximum length of time,using the test method under the specified conditions described later, inwhich a brush carrying the aqueous composition of the invention can beapplied to the edge region of a coating of the aqueous composition ofthe invention after which the coating flows back without leaving any laplines in the final dried coating, so as to result in a homogenous filmlayer.

Preferably the wet-edge time is at least 12 minutes, more preferably atleast 15 minutes, most preferably at least 18 minutes and especially atleast 25 minutes.

The drying process of an applied invention composition can be divided infour stages namely the periods of time necessary to achieverespectively, dust-free, tack-free, thumb-hard and sandable coatingsusing the tests described herein.

Preferably the dust free time is ≦21 hours, more preferably ≦16 hours,still more preferably ≦5 hours and especially ≦2 hours.

Preferably the tack-free time is ≦20 hours, more preferably ≦12 hoursand still more preferably ≦8 hours.

Preferably the thumb hard time is ≦48 hours, more preferably ≦24 hours,more preferably ≦16 hours and especially ≦10 hours.

Preferably the resultant coating is sandable within 72 hours, morepreferably within 48 hours, still more preferably within 24 hours andespecially within 16 hours.

A co-solvent, as is well known in the coating art, is an organic solventemployed in an aqueous composition to improve the drying characteristicsthereof. The invention composition can contain a co-solvent or a mixtureof co-solvents. More preferably the invention composition can containco-solvent or a mixture of co-solvents in a concentration ≦10%, morepreferably ≦5%, most preferably ≦3% and most especially 0% by weightbased on the invention composition. Preferably the co-solvent has amolecular weight below 200 g/mol. The co-solvent may be organic solventincorporated or used during preparation of the non-crosslinkableoligomer(s) and/or the dispersed polymer(s) or may have been addedduring formulation of the aqueous composition.

The equilibrium viscosity of the aqueous coating composition, whenmeasured under the conditions as described above, is a suitable methodfor illustrating the drying characteristics of the aqueous coatingcomposition. By the equilibrium viscosity of an aqueous composition at aparticular shear rate and solids content is meant the viscosity measuredwhen the aqueous composition has been subjected to the shear rate at forlong enough to ensure that the viscosity measurement has reached aconstant value.

If the composition is to remain brushable and workable during drying sothat it has the desired open time and wet edge time, it is necessarythat its equilibrium viscosity does not exceed defined limits during thedrying process and hence over a range of solids contents. Accordinglythe non-crosslinkable water-dispersible oligomer(s) which are used inthis invention do not give a significant phase inversion viscosity peak,if any at all, during the drying process when the system inverts fromone in which water is the continuous phase to one in which thecontinuous phase is a mixture of non-crosslinkable water-dispersibleoligomer(s), solvent and optionally (part of the) water.

The shear rate to measure the equilibrium viscosity is preferably anyshear rate in the range of from 0.9±0.05 to 90±5 s⁻¹, more preferablyany shear rate in the range of from 0.09±0.005 to 90±5 s⁻¹.

Preferably the equilibrium viscosity of the aqueous coating compositionof the invention is ≦1500 Pa·s, more preferably ≦500 Pa·s, especially≦100 Pa·s, and most especially ≦50 Pa·s when measured as defined above.

Preferably, the composition of the invention has an equilibriumviscosity ≦5,000 Pa·s when measured using any shear rate in the range offrom 0.09±0.005 to 90±5 s⁻¹, and an equilibrium viscosity of ≦3,000 Pa·swhen measured using any shear rate in the range of from 0.9±0.05 to 90±5s⁻¹, and an equilibrium viscosity of ≦1,500 Pa·s when measured using anyshear rate in the range of from 9±0.5 to 90±5 s⁻¹, at any solids contentwhen drying in the range of from 20 to 55% by weight of the compositionand at 23±2° C.

More preferably, the composition of the invention has an equilibriumviscosity of ≦3,000 Pa·s when measured using any shear rate in the rangeof from 0.09±0.005 to 90±5 s⁻¹, and an equilibrium viscosity of ≦1,500Pa·s when measured using any shear rate in the range of from 0.9±0.05 to90±6 s⁻¹, and an equilibrium viscosity of ≦500 Pa·s when measured usingany shear rate in the range of from 9±0.5 to 90±5 s⁻¹, at any solidscontent when drying in the range of from 20 to 55% by weight of thecomposition and at 23±±2° C.

Even more preferably, the composition of the invention has anequilibrium viscosity of ≦1,500 Pa·s when measured using any shear ratein the range of from 0.09±0.005 to 90±5 s⁻¹, and an equilibriumviscosity of ≦200 Pa·s when measured using any shear rate in the rangeof from 0.9±0.05 to 90±5 s⁻¹, and an equilibrium viscosity of ≦100 Pa·swhen measured using any shear rate in the range of from 9±0.5 to 90±5s⁻¹, at any solids content when drying in the range of from 20 to 55% byweight of the composition and at 23±2° C.

Preferably the solids content of the aqueous coating composition whendetermining the equilibrium viscosity is in the range of from 20 to 60%,more preferably in the range of from 20 to 70%, and especially in therange of from 20 to 80% by weight of the composition.

Preferably the equilibrium viscosity of the composition of the inventionis ≦5000 Pa·s, more preferably ≦3000 Pa·s when measured using any shearrange in the range of from 0.9±0.05 to 90±5 s⁻¹, more preferably usingany shear rate in the range of from 0.09±0.005 to 90±5 s⁻¹; after a 12%,preferably a 15% and most preferably an 18% increase in the solidscontent by weight of the composition when drying (e.g. a 12% increasemeans going from a solids content of 35 to 47% by weight of thecomposition).

In a preferred embodiment of the present invention the non-crosslinkableoligomer(s) has a solution viscosity ≦150 Pa·s, as determined from a 80%by weight solids solution of the non-crosslinkable oligomer(s) in atleast one of the solvents selected from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof, using a shearrate of 90±5 s⁻¹ and at 50±2° C.

A choice of solvents for determining the solution viscosity of thenon-crosslinkable oligomer(s) is provided herein because the nature ofthe non-crosslinkable oligomer(s) may affect its solubility.

Preferably the solution viscosity of the non-crosslinkable oligomer(s)is ≦100 Pa·s, especially ≦50 Pa·s and most especially ≦30 Pa·s whenmeasured as defined above.

Alternatively in this embodiment of the invention, and more preferably,the solution viscosity of the non-crosslinkable oligomer(s) may bemeasured at 23±2° C., and the non-crosslinkable oligomer(s) may thusalso be described as preferably having a solution viscosity ≦250 Pa·s,as determined from a 70% by weight solids solution of thenon-crosslinkable oligomer(s) in a solvent mixture consisting of:

i) at least one of the solvents selected from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof;

ii) water; and

iii) N,N-dimethylethanolamine;

where i), ii) and iii) are in weight ratios of 20/7/3 respectively,using a shear rate of 90±5 s⁻¹ and at 23±2° C.

Preferably in the preceding alternative the solution viscosity of thenon-crosslinkable oligomer(s) is ≦100 Pa·s, more especially ≦50 Pa·s,still more especially ≦35 Pa·s and most especially ≦20 Pa·s, whenmeasured as defined herein at 23±2° C.

If a mixture of N-methylpyrrolidone (NMP) and n-butylglycol (BG) isused, preferably the ratio of NMP:BG is in the range of from 0.01:99.9to 99.9:0.01, more preferably the ratio of NMP:BG is in the range offrom 0.01:99.9 to 10:90 and in the range of from 90:10 to 99.9:0.01, andmost preferably the ratio of NMP:BG is in the range of from 0.5:99.5 to5:95 and in the range of from 95:5 to 99.5:0.5.

The non-crosslinkable oligomer(s) may be completely water-soluble oronly have partial or low solubility in water. Preferably thenon-crosslinkable oligomer(s) only has partial or little solubility inwater. If the non-crosslinkable oligomer(s) is only partially or littlesoluble in water, it preferably has low water solubility in a pH rangeof from 2 to 10 and is either self-dispersible in water (i.e.dispersible by virtue of a sufficient concentration of selected bound(in-chain, chain-pendant and/or chain-terminal) hydrophilic groups builtinto the non-crosslinkable oligomer(s), and thus not requiring highshear techniques and/or added surfactants to produce the dispersion,although such methods can also be included if desired), or is onlydispersible in water with the aid of added (i.e. external) surfaceactive agents and/or the use of high shear mixing. Low water solubilityconfers the advantage of a reduced water-sensitivity of the appliedcoating. Such low water solubility is defined herein as thenon-crosslinkable oligomer(s) being less than 70% by weight soluble inwater throughout the pH range of from 2 to 10 as determined for exampleby a centrifuge test as described herein. Preferably thenon-crosslinkable oligomer(s) is ≦60%, more preferably ≦50% mostpreferably ≦30% by weight soluble in water throughout the pH range offrom 2 to 10. The non-crosslinkable oligomer(s) preferably contains asufficient concentration of bound hydrophilic water-dispersing groupscapable of rendering the oligomer(s) self-water-dispersible, but theconcentration of such groups is preferably not so great that theoligomer(s) has an unacceptably high water solubility in order to notcompromise the water sensitivity of the final coating.

The type of hydrophilic groups capable of rendering thenon-crosslinkable oligomer(s) self-water-dispersible are well known inthe art, and can be ionic water-dispersing groups or non-ionicwater-dispersing groups. Preferred non-ionic water-dispersing groups arepolyalkylene oxide groups, more preferably polyethylene oxide groups. Asmall segment of the polyethylene oxide group can be replaced bypropylene oxide segment(s) and/or butylene oxide segment(s), however thepolyethylene oxide group should still contain ethylene oxide as a majorcomponent. When the water-dispersible group is polyethylene oxide, theethylene oxide group preferably has a Mw from 175 to 5000 Daltons, morepreferably from 350 to 2200 Daltons, most preferably from 660 to 1100Daltons. Preferably the non-crosslinkable oligomer(s) has a polyethyleneoxide content of 0 to 50% by weight, more preferably 0 to 39% by weightand most preferably 2 to 35% by weight.

Preferred ionic water-dispersing groups are anionic water-dispersinggroups, especially carboxylic, phosphoric and or sulphonic acid groups.The anionic water-dispersing groups are preferably fully or partially inthe form of a salt. Conversion to the salt form is optionally effectedby neutralisation of the non-crosslinkable oligomer(s) with a base,preferably during the preparation of the non-crosslinkable oligomer(s)and/or during the preparation of the composition of the presentinvention. The anionic dispersing groups may in some cases be providedby the use of a monomer having an already neutralised acid group in thenon-crosslinkable oligomer(s) synthesis so that subsequentneutralisation is unnecessary. If anionic water-dispersing groups areused in combination with non-ionic water-dispersing groups,neutralisation may not be required.

If the anionic water-dispersing groups are neutralised, the base used toneutralise the groups is preferably ammonia, an amine or an inorganicbase. Suitable amines include tertiary amines, for example triethylamineor N,N-dimethylethanolamine. Suitable inorganic bases include alkalihydroxides and carbonates, for example lithium hydroxide, sodiumhydroxide, or potassium hydroxide. A quaternary ammonium hydroxide, forexample N⁺(CH₃)₄OH⁻, can also be used. Generally a base is used whichgives counter ions that may be desired for the composition. For example,preferred counter ions include Li⁺, Na⁺, K⁺, NH₄ ⁺ and substitutedammonium salts.

Cationic water dispersible groups can also be used, but are lesspreferred. Examples include pyridine groups, imidazole groups and orquaternary ammonium groups which may be neutralised or permanentlyionised (for example with dimethylsulphate).

The non-crosslinkable oligomer(s) may be dispersed in water usingtechniques well known in the art. Preferably, the non-crosslinkableoligomer(s) is added to the water with agitation or, alternatively,water may be stirred into the non-crosslinkable oligomer(s).

Surfactants and/or high shear can be utilised in order to assist in thedispersion of the non-crosslinkable, water-dispersible oligomer(s) inwater (even if it is self-dispersible). Suitable surfactants include butare not limited to conventional anionic, cationic and/or non-ionicsurfactants such as Na, K and NH₄ salts of dialkylsulphosuccinates, Na,K and NH₄ salts of sulphated oils, Na, K and NH₄ salts of alkylsulphonic acids, Na, K and NH₄ alkyl sulphates, alkali metal salts ofsulphonic acids; fatty alcohols, ethoxylated fatty acids and/or fattyamides, and Na, K and NH₄ salts of fatty acids such as Na stearate andNa oleate. Other anionic surfactants include alkyl or (alk)aryl groupslinked to sulphonic acid groups, sulphuric acid half ester groups(linked in turn to polyglycol ether groups), phosphonic acid groups,phosphoric acid analogues and phosphates or carboxylic acid groups.Cationic surfactants include alkyl or (alk)aryl groups linked toquaternary ammonium salt groups. Non-ionic surfactants includepolyglycol ether compounds and polyethylene oxide compounds. The amountof surfactant used is preferably 0 to 15% by weight, more preferably 0to 8% by weight, still more preferably 0 to 5% by weight, especially 0.1to 3% by weight, and most especially 0.3 to 2% by weight based on theweight of the non-crosslinkable oligomer(s).

The non-crosslinkable oligomer(s) preferably has a measured weightaverage molecular weight (Mw) in the range of from 1000 to 80,000Daltons and more preferably in the range of from 1500 to 50,000 Daltons.If a branched non-crosslinkable oligomer(s) is used, higher molecularweight limits are preferred as branched structures tend to give a lowerviscosity than a linear structure for any given Mw. For the purpose ofthis invention any molecular species with a molecular weight <1000Daltons is classified as either a reactive diluent or a plasticiser andis therefore not taken into account for the determination of Mn, Mw orPDi. Plasticisers are defined as liquid compounds with a molecularweight of 200 to 1000 g/mole.

Preferably the amount of plasticiser % by weight based on the solidscontent of the composition is ≦15 wt %, preferably ≦8 wt %, morepreferably ≦3 wt % and most preferably 0 wt %.

The molecular weight distribution (MWD) of the non-crosslinkableoligomer(s) has an influence on the equilibrium viscosity of the aqueouscomposition of the invention, and hence an influence on the open time.MWD is conventionally described by the polydispersity index (PDi). PDiis defined as the weight average molecular weight divided by the numberaverage molecular weight (Mw/Mn) where lower values are equivalent tolower PDi's. It has been found that a lower PDi often results in lowerviscosities for a given Mw non-crosslinkable oligomer(s). Preferably thevalue of PDi of the non-crosslinkable oligomer(s) is ≦15, morepreferably ≦10, and most preferably ≦5. In a preferred embodiment thevalue of Mw×PDi^(0.8) of the non-crosslinkable oligomer(s) is ≦220,000,more preferably the Mw×PDi^(0.8) is ≦100,000 and most preferably theMw×PDi^(0.8) is ≦50,000.

The non-crosslinkable oligomer(s) preferably has an acid value of in therange of from 0 to 80 mg KOH/g, more preferably in the range of from 0to 35 mgKOH/g, still more preferably in the range of from 0 to 30 mgKOH/g and most preferably in the range of from 2 to 30 mg KOH/g.

The glass transition temperature (Tg) of the non-crosslinkableoligomer(s) may vary within a wide range. The Tg (as measured bymodulated DSC) is preferably in the range of from −120 to 250° C., morepreferably in the range of from −120 to 100° C., still more preferablyin the range of from −70 to 70° C., especially in the range of from −50to 20° C.

The non-crosslinkable oligomer(s) may comprise a singlenon-crosslinkable oligomer or a mixture of non-crosslinkable oligomers.Non-crosslinkable oligomer(s) include but are not limited to for examplepolyurethane oligomer(s), vinyl oligomer(s), polyamide oligomer(s),polyether oligomer(s), polysiloxane oligomer(s) and/or polyesteroligomer(s) and the non-crosslinkable oligomer(s) may optionally bebranched (such branched oligomer(s) may also be known as hyperbranchedmacromolecule(s)).

Preferably the composition of the invention comprises no substantialamount of a crosslinkable oligomer(s), most preferably the compositionof the invention comprises 0 to <0.4 wt % of a crosslinkableoligomer(s), provided that the crosslinkable oligomer(s) has a solutionviscosity and/or a Mw within the preferred ranges defined above for thenon-crosslinkable oligomer(s).

The water-dispersible non-crosslinkable oligomer(s), if a polyurethaneoligomer(s), may be prepared in a conventional manner by reacting anorganic polyisocyanate with an isocyanate reactive compound.

Methods for preparing polyurethanes are known in the art and aredescribed in for example the Polyurethane Handbook 2^(nd) Edition, aCarl Hanser publication, 1994, by G. Oertel; and these methods areincluded herein by reference. Isocyanate-reactive groups include —OH,—SH, —NH—, and —NH₂. In some preparations, an isocyanate-terminatedpolyurethane prepolymer is first formed which is then chain extendedwith an active hydrogen containing compound.

Suitable polyisocyanates include aliphatic, cycloaliphatic, araliphaticand/or aromatic polyisocyanates. Examples of suitable polyisocyanatesinclude ethylene diisocyanate, 1,6-hexamethylene diisocyanate,isophorone diisocyanate, cyclohexane-1,4-diisocyanate,4,4′-dicyclohexylmethane diisocyanate, p-xylylene diisocyanate,α,α′-tetramethylxylene diisocyanate, 1,4-phenylene diisocyanate,2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4′-diphenylmethanediisocyanate, polymethylene polyphenyl polyisocyanates,2,4′-diphenylmethane diisocyanate, 3(4)-isocyanatomethyl-1-methylcyclohexyl isocyanate and 1,5-naphthylene diisocyanate. Mixtures ofpolyisocyanates can be used and also polyisocyanates which have beenmodified by the introduction of urethane, allophanate, urea, biuret,carbodiimide, uretonimine, urethdione or isocyanurate residues.

Hydrophilic water-dispersing groups, if present, are preferablyintroduced by employing as a reactant(s) in the urethane synthesis atleast one isocyanate-reactive compound (or less preferably anisocyanate-functional compound(s)) bearing a non-ionic and/or ionichydrophilic water-dispersing group(s) (as described above) (or groupwhich may be subsequently easily converted to such a water-dispersinggroup, e.g. by neutralisation, such a group still being termed awater-dispersing group for the purposes of this invention) as a reactantin the preparation of the polyurethane oligomer or prepolymer. Examplesof such compounds include carboxyl group containing diols and triols,for example dihydroxy alkanoic acids such as 2,2-dimethylolpropionicacid or 2,2-dimethylolbutanoic acid. Examples of preferred compoundsbearing non-ionic hydrophilic water-dispersing groups include methoxypolyethylene glycol (MPEG) with molecular weights of for example 350,550, 750, 1000 and 2000, as described in EP 0317258.

Other isocyanate-reactive organic compounds bearing no hydrophilicwater-dispersing groups which may be used in the preparation ofnon-crosslinkable polyurethane oligomer(s) or polyurethane prepolymerspreferably contain at least one (preferably at least two)isocyanate-reactive groups, and are more preferably organic polyols. Theorganic polyols particularly include diols and triols and mixturesthereof but higher functionality polyols may be used, for example asminor components in admixture with diols. The polyols may be members ofany of the chemical classes of polyols used or proposed to be used inpolyurethane formulations. In particular the polyols may be polyesters,polyesteramides, polyethers, polythioethers, polycarbonates,polyacetals, polyolefins or polysiloxanes. Preferred polyol molecularweights are from 250 to 6000, more preferably from 500 to 3000. Lowmolecular weight organic compounds containing at least one (preferablyat least two) isocyanate-reactive groups and having a weight averagemolecular weight up to 500, preferably in the range of 40 to 250 canalso be used. Examples include ethyleneglycol, neopentyl glycol,1-propanol, and 1,4-cyclohexyldimethanol.

When an isocyanate-terminated polyurethane prepolymer is prepared, it isconventionally formed by reacting a stoichiometric excess of the organicpolyisocyanate with the isocyanate-reactive compounds undersubstantially anhydrous conditions at a temperature between about 30° C.and about 130° C. until reaction between the isocyanate groups and theisocyanate-reactive groups is substantially complete; the reactants forthe prepolymer are generally used in proportions corresponding to aratio of isocyanate groups to isocyanate-reactive groups of from about1.1:1 to about 6:1, preferably from about 1.5:1 to 3:1.

Alternatively a hydroxyl-terminated non-crosslinkable polyurethaneoligomer(s) may be prepared directly by reacting the reactants inproportions corresponding to a ratio of isocyanate groups toisocyanate-reactive groups of from about 0.4:1 to about 0.99:1,preferably from about 0.55:1 to 0.95:1.

A non-crosslinkable polyurethane oligomer(s) of acceptably low Mw may bemade by capping an isocyanate-terminated polyurethane oligomer(s) with amonofunctional isocyanate-reactive compound or by using a stoichiometricexcess of reactant(s) having isocyanate-reactive groups during theoligomer preparation, thereby forming an isocyanate-reactive group(preferably —OH) terminated non-crosslinkable polyurethane oligomer. Acombination of both techniques may be used.

If desired, catalysts such as dibutyltin dilaurate and stannous octoate,zirconium or titanium based catalysts may be used to assist thenon-crosslinkable polyurethane oligomer(s) formation. An organic solventmay optionally be added before or after prepolymer or final oligomerformation to control the viscosity. Examples of solvents includewater-miscible solvents such as N-methylpyrrolidone, dimethyl acetamide,glycol ethers such as butyidiglycol, 2-propanone and alkyl ethers ofglycol acetates or mixtures thereof. Optionally no organic solvents areadded.

An aqueous non-crosslinkable polyurethane oligomer(s) dispersion mayalso be prepared, when the prepolymer/chain extension route wasemployed, by dispersing the isocyanate-terminated polyurethaneprepolymer (optionally carried in an organic solvent medium) in anaqueous medium and chain extending the prepolymer with activehydrogen-containing chain extender in the aqueous phase.

Active hydrogen-containing chain extenders which may be reacted with theisocyanate-terminated polyurethane prepolymer include amino-alcohols,primary or secondary diamines or polyamines, hydrazine, and substitutedhydrazines.

Examples of such chain extenders useful herein include alkylene diaminessuch as ethylene diamine and cyclic amines such as isophorone diamine.Also materials such as hydrazine, azines such as acetone azine,substituted hydrazines such as, for example, dimethyl hydrazine,1,6-hexamethylene-bis-hydrazine, carbodihydrazine, hydrazides ofdicarboxylic acids and sulphonic acids such as adipic acid mono- ordihydrazide, oxalic acid dihydrazide, isophthalic acid dihydrazide,hydrazides made by reacting lactones with hydrazine such asgammahydroxylbutyric hydrazide, bis-semi-carbazide, and bis-hydrazidecarbonic esters of glycols may be useful. Water itself may be effectiveas an indirect chain extender.

Where the chain extender is other than water, for example a polyamine orhydrazine, it may be added to the aqueous dispersion of theisocyanate-terminated polyurethane prepolymer or, alternatively, it mayalready be present in the aqueous medium when the isocyanate-terminatedpolyurethane prepolymer is dispersed therein.

Optionally a combination of chain extender(s) and chain terminator(s)may be used. Examples of chain terminators are mono-functionalisocyanate-reactive compounds such as mono-alcohols, mono-amines,mono-hydrazines and mono-mercaptanes. The ratio of chain extender tochain terminator compounds is preferably in the range of from 95:5 to5:95, more preferably 50:50 to 10:90 and most preferably 35:65 to 20:80.

The chain extension and/or chain termination can be conducted atelevated, reduced or ambient temperatures. Convenient temperatures arefrom about 5° C. to 95° C. or, more preferably, from about 10° C. to 60°C.

The total amount of chain extender and chain terminating materialsemployed (apart from water) should be such that the ratio of activehydrogens in the chain extender(s) to isocyanate groups in thepolyurethane prepolymer preferably is in the range from 0.1:1 to 2.0:1more preferably 0.8:1 to 1.7:1.

Any other known methods for preparing polyurethane dispersions such as aketamine/ketazine process or a hot process as described in “Progress inOrganic Coatings”, D. Dietrich, 9, 1981, p 281) may also be utilised.

The non-crosslinkable polyurethane oligomer(s) has preferably has ameasured weight average molecular weight (Mw) in the range of from 1500to 60,000 Daltons, more preferably in the range of from 2,500 to 40,000Daltons, and most preferably in the range of from 5,000 to 25,000Daltons.

Preferably the non-crosslinkable polyurethane oligomer(s) has apolyethylene oxide content of 0 to 45% by weight, more preferably 0 to25% by weight and most preferably 2 to 15% by weight.

The non-crosslinkable polyurethane oligomer(s) preferably has at leastone glass transition temperature (Tg) in the range of from −100 to 250°C., more preferably −80 to 50° C. and most preferably −70 to 10° C. andespecially −50 to 0° C.

The non-crosslinkable polyurethane oligomer(s) preferably has an acidvalue in the range of from 0 to 50 mg KOH/g, more preferably in therange of from 0 to 40 mg KOH/g and most preferably in the range of from10 to 30 mg KOH/g.

The non-crosslinkable water-dispersible oligomer(s) if a polyesteroligomer(s) can be prepared using conventional polymerisation proceduresknown to be effective for polyester synthesis. General processes for thepreparation of polyesters are described in “Alkyd Resin Technology” by TC Patton, Publisher John Wiley & sons Inc. (1962). It is known thatpolyesters, which contain carbonyloxy (i.e. —C(═O)—O—) linking groupsmay be prepared by a condensation polymerisation process in whichmonomer(s) providing an “acid component” (including ester-formingderivatives thereof) is reacted with monomer(s) providing a “hydroxylcomponent”. The monomer(s) providing an acid component may be selectedfrom one or more polybasic carboxylic acids such as di- ortri-carboxylic acids or ester-forming derivatives thereof such as addhalides, anhydrides or esters. The monomer(s) providing a hydroxylcomponent may be one or more polyhydric alcohols or phenols (polyols)such as diols, triols, etc. Mono-functional acid and hydroxy componentsmay also be included in the preparation of the non-crosslinkablepolyester oligomer(s). (It is to be understood, however, that thenon-crosslinkable polyester oligomer(s) may contain, if desired, aproportion of carbonylamino linking groups —C(═O)—NH— (i.e. amidelinking group) by including an appropriate amino functional reactant aspart of the “hydroxyl component” or alternatively all of the hydroxylcomponent may comprise amino functional reactants, thus resulting in apolyamide oligomer; such amide linkages are in fact useful in that theyare more hydrolysis resistant).

There are many examples of carboxylic acids (or their ester formingderivatives) which can be used in non-crosslinkable polyesteroligomer(s) synthesis for the provision of the monomer(s) providing anacid component. Examples include, but are not limited to C₂ to C₂₂monocarboxylic acids such as (alkylated) benzoic acid and hexanoic acid;and C₄ to C₂₀ aliphatic, alicyclic and aromatic dicarboxylic acids (orhigher functionality acids) or their ester-forming derivatives (such asanhydrides, acid chlorides, or lower alkyl esters). Specific examplesinclude adipic acid, fumaric acid, maleic acid, succinic acid, itaconicacid, azeleic acid, sebacic acid, nonanedioic acid, decanedioic acid,1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid,1,2-cyclohexanedicarboxylic acid, terephthalic acid, fatty acid dimers,isophthalic acid, 5-sodiosulpho isophthalic acid, phthalic acid andtetrahydrophthalic acid. Anhydrides include succinic, maleic, phthalic,trimellitic and hexahydrophthalic anhydrides.

Similarly there are many examples of polyols which may be used innon-crosslinkable polyester oligomer(s) synthesis for the provision ofthe monomer(s) providing a hydroxyl component. The polyol(s) preferablyhave from 1 to 6 (more preferably 2 to 4) hydroxyl groups per molecule.Suitable monofunctional alcohols include for example eicosanol andlauryl alcohol. Suitable polyols with two hydroxy groups per moleculeinclude diols such as 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol,1,6-hexanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), the1,2-, 1,3- and 1,4-cyclohexanediols and the corresponding cyclohexanedimethanols, diethylene glycol, dipropylene glycol, and diols such asalkoxylated bisphenol A products, e.g. ethoxylated or propoxylatedbisphenol A. Suitable polyols with three hydroxy groups per moleculeinclude triols such as trimethylolpropane (TMP) and1,1,1-tris(hydroxymethyl)ethane (TME). Suitable polyols with four ormore hydroxy groups per molecule include bis-TMP, pentaerythritol(2,2-bis(hydroxymethyl)-1,3-propanediol), bis-pentaerythritol andsorbitol (1,2,3,4,5,6-hexahydroxyhexane).

Suitable compounds bearing non-ionic hydrophilic water dispersing groupsinclude for example ethylene oxide-containing hydroxy functionalcompounds such as alkoxypolyethlene glycols and polyethylene glycols.Preferably the hydrophilic water-dispersing groups are carboxylic acidgroups, sulphonic acid groups or sulphonate anion groups (neutralisationof the sulphonic acid groups preferably already having been effected.Preferably incorporation of carboxylic acid groups can occur by having aresidual carboxylic acid functionality, post functionalisation ofhydroxy-functionalised polyester oligomer(s) or use of stericallyhindered hydroxy functional acids such as dimethylolpropionic acid.Preferably, the sulphonic acid or sulphonate anion containing monomer isa dicarboxylic acid monomer having at least one sulphonic acid saltgroup substituent. Alternatively, alkyl ester groups may be used inplace of the carboxylic acid groups. Such a monomer will therefore bepart of the acid component used in the polyester synthesis. Examples ofsuch compounds are the alkali metal salts of sulphonic acid substitutedaromatic dicarboxylic acids, for example alkali metal salts of5-sulpho-1,3-benzene dicarboxylic acid. Particularly preferred issodio-5-sulphoisophthalic acid (SSIPA). Other useful sulphonic acidcontaining monomers are the alkali metal salts of sulphonic acidsubstituted aromatic dicarboxylic acid-dihydroxyalkylesters such as thealkali metal salts of 5-sulpho-1,3-benzenedicarboxylicacid-1,3-bis(2-hydroxyethyl)ester.

Preferably the ionic sulphonate water-dispersing group content of thenon-crosslinkable polyester oligomer(s) is in the range of from 7.5 to100 milliequivalents of ionic water-dispersing groups per 100 g ofnon-crosslinkable polyester oligomer(s), more preferably from 10 to 75milliequivalents per 100 g. Preferably the acid value of thenon-crosslinkable polyester oligomer(s) is in the range of from 0 to 80mgKOH/g, more preferably in the range of from 1 to 40 mgKOH/g, andespecially in the range of from 3 to 25 mgKOH/g.

Preferably the non-crosslinkable polyester oligomer(s) has apolyethylene oxide content of 0 to 50% by weight, more preferably 0 to45% by weight, still more preferably 0 to 38% by weight, especially 3 to35% by weight and most preferably 5 to 25% by weight. Thenon-crosslinkable polyester oligomer(s) preferably has a weight averagemolecular weight (Mw) in the range of from 1500 to 80,000 Daltons, morepreferably in the range of from 2000 to 65,000 Daltons, most preferablyin the range of from 3,500 to 50,000 Daltons, and especially in therange of from 5000 to 40,000 Daltons.

Preferably the non-crosslinkable polyester oligomer(s) has a Tg in therange of from −90 to 100° C., more preferably in the range of from −70to 40° C. and most preferably in the range of from −60 to 20° C.

An organic solvent may optionally be added before or after thepolymerisation process to control the viscosity.

The esterification polymerisation processes for making thenon-crosslinkable polyester oligomer(s) for use in the inventioncomposition are well known in the art and need not be described here indetail. Suffice to say that they are normally carried out in the meltusing catalysts such as tin-based catalysts and with the provision forremoving any water (or alcohol) formed from the condensation reaction.

The non-crosslinkable polyester oligomer(s) may be dispersed in waterusing techniques well known in the art. An aqueous dispersion of thenon-crosslinkable polyester oligomer(s) may be readily prepared byadding water directly to the hot non-crosslinkable polyester oligomer(s)melt until the desired solids content/viscosity is reached.Alternatively the non-crosslinkable polyester oligomer(s) may bedispersed in water by adding an aqueous pre-dispersion (or organicsolvent solution) of the polyester oligomer(s) to the water phase. Stillfurther an aqueous dispersion may be prepared by dispersion of thesolidified melt from the condensation polymerisation directly intowater. The solidified melt is preferably in a form such as flake (whichcan often be obtained directly from the melt) or comminuted solid(obtained for example by grinding).

The non-crosslinkable, water-dissipatable oligomer(s) if a vinyloligomer(s) is usually derived from free radically polymerisableolefinically unsaturated monomer(s), and can contain polymerised unitsof a wide range of such monomers, especially those commonly used to makebinders for the coatings industry. By a vinyl oligomer herein is meant ahomo- or co-oligomer derived from the addition polymerisation (using afree radical initiated process which may be carried out in an aqueous ornon-aqueous medium) of one or more olefinically unsaturated monomers.Therefore by a vinyl monomer is meant an olefinically unsaturatedmonomer.

A particularly preferred non-crosslinkable vinyl oligomer(s) is anacrylic oligomer(s) (i.e. based predominantly on at least one ester ofacrylic or methacrylic acid).

Examples of vinyl monomers which may be used to form a non-crosslinkablevinyl oligomer include but are not limited to 1,3-butadiene, isoprene,styrene, α-methyl styrene, divinyl benzene, acrylonitrile,methacrylonitrile, vinyl halides such as vinyl chloride, vinylidenehalides such as vinylidene chloride, vinyl ethers, vinyl esters such asvinyl acetate, vinyl propionate, vinyl laurate, and vinyl esters ofversatic acid such as VeoVa 9 and VeoVa 10 (VeoVa is a trademark ofShell), heterocyclic vinyl compounds, alkyl esters of mono-olefinicallyunsaturated dicarboxylic acids (such as di-n-butyl maleate anddi-n-butyl fumarate) and, in particular, esters of acrylic acid andmethacrylic acid of formulaCH₂═CR¹—COOR²wherein R¹ is H or methyl and R² is optionally substituted alkyl orcycloalkyl of 1 to 20 carbon atoms (more preferably 1 to 8 carbon atoms)examples of which are methyl acrylate, methyl methacrylate, ethylacrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate,2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isopropyl acrylate,isopropyl methacrylate, n-propyl acrylate, n-propyl methacrylate, andhydroxyalkyl (meth)acrylates such as hydroxyethyl acrylate, hydroxyethylmethacrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate,4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate and their modifiedanalogues like Tone M-100 (Tone is a trademark of Union CarbideCorporation).

Particularly preferred is a non-crosslinkable vinyl oligomer made from amonomer system comprising at least 40 weight % of one or more monomersof the formula CH₂═CR¹COOR² as defined above. Such a preferrednon-crosslinkable vinyl oligomer is defined herein as anon-crosslinkable acrylic oligomer. More preferably, the monomer systemcontains at least 50 wt. % of such monomers, and particularly at least60 wt. %. The other monomer(s) in such acrylic oligomer(s) (if used) mayinclude one or more of the other vinyl monomers mentioned above, and/ormay include ones different to such other monomers. Particularlypreferred monomers include butyl acrylate (all isomers), butylmethacrylate, methyl methacrylate, ethyl hexyl methacrylate, esters of(meth)acrylic acid, acrylonitrile, vinyl acetate and styrene.

The hydrophilic water-dispersing groups may be introduced by for examplei) utilising in the synthesis of the non-crosslinkable vinyl oligomer(s)a vinyl monomer which carries a hydrophilic water-dispersing group (forexample an olefinically unsaturated monocarboxylic, sulphonic and/ordicarboxylic acid, such as acrylic acid, methacrylic acid, carboxyethylacrylate, fumaric acid or itaconic acid, an amide such as(meth)acrylamide, or a polyethyleneoxide containing (meth)acrylatemonomer such as methoxy(polyethyleneoxide (meth)acrylate) or ahydroxyalkyl(meth)acrylate like hydroxyethyl(meth)acrylate HE(M)A, oralternatively ii) utilising a precursor vinyl oligomer bearing selectivereactive groups which is subsequently reacted with a compound carrying awater-dispersing group to provide attachment of the water-dispersinggroup to the oligomer via covalent bonding.

The non-crosslinkable vinyl oligomer(s) is preferably prepared by freeradical polymerisation, although in some circumstances anionicpolymerisation may be utilised. The free radical polymerisation can beperformed by techniques known in the art, for example by emulsionpolymerisation, solution polymerisation, suspension polymerisation orbulk polymerisation.

A free-radical polymerisation of vinyl monomer(s) to form anon-crosslinkable vinyl oligomer(s) will require the use of afree-radical-yielding initiator(s) to initiate the vinyl monomerpolymerisation. Suitable free-radical-yielding initiators includeinorganic peroxides such as K, Na or ammonium persulphate, hydrogenperoxide, or percarbonates; organic peroxides, such as acyl peroxidesincluding e.g. benzoyl peroxide, alkyl hydroperoxides such as t-butylhydroperoxide and cumene hydroperoxide; dialkyl peroxides such asdi-t-butyl peroxide; peroxy esters such as t-butyl perbenzoate and thelike; mixtures may also be used. The peroxy compounds are in some casesadvantageously used in combination with suitable reducing agents (redoxsystems) such as Na or K pyrosulphite or bisulphite, and iso-ascorbicacid. Azo compounds such as azoisobutyronitrile may also be used. Metalcompounds such Fe.EDTA (EDTA is ethylene diamine tetracetic acid) mayalso be usefully employed as part of the redox initiator system. It ispossible to use an initiator system partitioning between the aqueous andorganic phases, e.g. a combination of t-butyl hydroperoxide,iso-ascorbic acid and Fe.EDTA. The amount of initiator or initiatorsystem to use is conventional, e.g. within the range 0.05 to 6 wt. %based on the total vinyl monomer(s) used.

As stated above, a preferred feature of the invention is a low solutionviscosity for the vinyl oligomer(s) (as defined) which may be obtainedby controlling the molecular weight and/or the MWD of thenon-crosslinkable vinyl oligomer(s).

It may be desirable to control the molecular weight by addition of achain transfer agent to the free radical polymerisation process.Conventional chain transfer agents may be utilised and includemercaptans, sulphides, disulphides, triethylamine and halocarbons. Inparticular however the technique known as catalytic chain transferpolymerisation (CCTP) may be used to provide low molecular weights. Inthis case a free radical polymerisation is carried out using a freeradical forming initiator and a catalytic amount of a selectedtransition metal complex acting as a catalytic chain transfer agent(CCTA), and in particular a selected cobalt chelate complex. Such atechnique has been described for example in N. S. Enikolopyan et al, J.Polym. Chem. Ed., Vol 19, 879 (1981), U.S. Pat. No. 4,526,945, U.S. Pat.No. 4,680,354, EP-A-0196783, EP-A-0199436, EP-A-0788518 andWO-A-87/03605.

The use of catalytic chain transfer agents provide important benefitssuch as such as a) very low concentrations of catalytic chain transferagent (typically 1 to 1000 ppm by weight of vinyl monomer used) arerequired to attain the preferred low molecular weight oligomer and donot have the odour often associated with conventional chain transferagents;

b) CCTP allows the preparation of a vinyl oligomer(s) which has anarrower PDi than is achievable by the use of conventional chaintransfer agents for low Mw oligomer(s). As discussed above, low PDifavours low viscosity in the bulk and in solution (for a given Mw),which in turn leads to longer open time and wet edge time.

The non-crosslinkable vinyl oligomer(s) of the composition of theinvention preferably has an acid value of in the range of from 0 to 80mg KOH/g, more preferably in the range of from 0 to 30 mg KOH/g mostpreferably in the range of from 5 to 15 mg KOH/g.

The glass transition temperature (Tg) of the non-crosslinkable vinyloligomer(s) is preferably in the range of from −90 to 120° C., morepreferably in the range of from −70 to 60° C. Particularly preferred isthat the Tg of the non-crosslinkable vinyl oligomer(s) is in the rangeof from −60 to 30° C., more preferably in the range of from −50 to 0° C.

Preferably the non-crosslinkable vinyl oligomer(s) has a polyethyleneoxide content of 0 to 45% by weight, more preferably 0 to 30% by weightand still more preferably 2 to 20% by weight and especially 3 to 15% byweight.

The non-crosslinkable vinyl oligomer(s) preferably has a weight averagemolecular weight (Mw) in the range of from 2,000 to 80,000 Daltons, morepreferably in the range of from 3,000 to 50,000 Daltons, still morepreferably in the range of from 4000 to 30,000 Daltons, and mostpreferably in the range of from 5,000 to 25,000 Daltons.

The non-crosslinkable, water-dispersible oligomer(s) if a hyperbranchedmacromolecule(s) may be prepared by controlled step-growth(condensation) polymerisation and uncontrolled chain-growth (addition)polymerisation. Methods for preparing hyperbranched or dendriticmolecules are known in the art and are described in for example inTomalia et al (Angewandte Chemie International Edition English, 1990,Vol 29, pp 138–175) and the Encyclopaedia of Polymer Science andEngineering, Volume Index 1990, pp 46–92. Methods for preparinghyperbranched macromolecule(s) are also reviewed in U.S. Pat. No.5,418,301, U.S. Pat. No. 5,663,247, WO 96/19537, WO 96/13558, U.S. Pat.No. 5,270,402, U.S. Pat. No. 5,136,014, U.S. Pat. No. 5,183,862, WO93/18079, U.S. Pat. No. 5,266,106 and U.S. Pat. No. 5,834,118 and thesemethods are included herein by reference.

The non-crosslinkable hyperbranched macromolecule(s) are often derivedfrom a nucleus (or core molecule) having one or more reactive groups towhich successive groups of branching and/or chain-extender moleculeshaving at least two reactive groups are added to form branches. Eachsuccessive group of branching and/or chain-extender molecules isnormally known as a generation. The branches may then bechain-terminated by adding a chain-terminator molecule(s) having onereactive group that is reactive towards a reactive group on the branch.Alternatively the branches can be made first and linked togetherafterwards to give the hyperbranched macromolecule(s).

When preparing non-crosslinkable hyperbranched macromolecule(s) somedefects are possible and these include inter-macromolecule defects andintra-macromolecule defects such as bridging or looping.Intra-macromolecule defects decrease branching symmetry andinter-macromolecule defects lead to more polydisperse systems. Theseevents may be minimised or eliminated if desired by process optimisationand synthetic strategy optimisation.

The size, shape and properties of hyperbranched macromolecule(s) can becontrolled by the choice of the core molecule, the number ofgenerations, the degree of branching and the choice and amount ofchain-extender and chain-terminator molecules employed.

The core molecule may affect the hyperbranched macromolecule(s) shape,producing for example spheroid-, comb- cylindrical- or ellipsoid-shapedhyperbranched macromolecule(s). The sequential building of generationsdetermines the nature, function and dimensions of the hyperbranchedmacromolecule(s).

Examples of core molecules include but are not limited to moleculeshaving one or more carboxylic acid groups (including monofunctionalcarboxylic acids having at least two hydroxyl groups such asdimethylolpropionic acid), amine groups (including ammonia,polyfunctional amines, such as ethylene diamine, linear and/or branchedpolyethyleneimines), halide groups, hydroxyl groups (including mono- andpolyfunctional alcohols such as pentaerythritol, dipentaerythritol,alkyl glucosides, neopentyl glycol, tris(hydroxymethyl)ethane,trimethylolpropane (TMP), bis-TMP, sorbitol, mannitol, sacharides, sugaralcohols, 1,1,1-tris-(4′-hydroxyphenyl)-ethane, 3,5-dihydroxy-benzylalcohol) or epoxide groups.

Examples of chain-extender molecules include but are not limited todiisocyanates, diethylene diimine, diols, and carboxylic anhydrides.Examples of branching molecules include but are not limited to, forexample, 3,5-dihydroxy-benzyl alcohol; monofunctional carboxylic acidshaving at least two hydroxyl groups, such as dimethylolpropionic acid,and dimethylolbutanoic acid, hydroxy functional diacids (or theiresters) such as aspartate esters, 5-hydroxy-isophthalic acid, but mayalso be indirectly obtained, for example through two Michael additionsof an acrylate ester or acrylonitrile to one primary amine functionalgroup, or through reaction of a carboxylic acid functional anhydridesuch as trimellitic anhydride (TMA) with an OH functional group, whichresults in a diacid functional group. Preferably, the reactive groupswithin each of the chain-extender and branching molecules have adifferent reactivity to reduce the amount of crosslinking duringsynthesis between the individual hyperbranched molecules, i.e. tocontrol the polydispersity.

Examples of chain-terminator molecules include but are not limited tomono-functional molecules (or oligomers) carrying for example epoxide,isocyanate, hydroxyl, thiol, carboxylate, carboxylic anhydride, ester,amides, phosphates, amino, sulphonate and carboxylic acid groups (suchas benzoic acid and (meth)acrylic acid, which react with the reactivegroups on the periphery of the hyperbranched macromolecule(s).

The chain-extender and or chain-terminator molecules may carryhydrophilic water-dispersing groups which may be introduced directly inthe non-crosslinkable hyperbranched macromolecule(s) by condensationpolymerisation, or alternatively hydrophilic water-dispersing groups maybe reacted onto the non-crosslinkable hyperbranched macromolecule(s) byany known technique.

Suitable reactive groups of the molecules used in the preparation ofnon-crosslinkable hyperbranched macromolecule(s) usually include but arenot limited to hydroxyl, carboxylic acid, epoxide, amine, allyl,acryloyl, carboxylic esters, carboxylic anhydrides, silanes, nitriles(which after reduction give amines) and oxazolines.

Hydrophilic water-dispersing groups may be introduced into thenon-crosslinkable hyperbranched macromolecule(s) using two generalmethods: i) by utilising in the polymerisation process to form ahyperbranched macromolecule(s), a branching molecule, a chain-extendermolecule and/or chain-terminator molecule carrying hydrophilicwater-dispersing groups; and ii) utilising a molecule chain-extenderand/or chain-terminator molecule bearing selected reactive groups andwhich molecule is subsequently reacted with a molecule carrying ahydrophilic water-dispersing groups and also a reactive group of thetype which will react with the selected reactive groups on thenon-crosslinkable hyperbranched macromolecule(s) to provide attachmentof the hydrophilic water-dispersing groups to the non-crosslinkablehyperbranched macromolecule(s) via covalent bonding.

The non-crosslinkable hyperbranched macromolecule(s) preferably has anacid value of in the range of from 0 to 80 mg KOH/g, more preferably inthe range of from 0 to 50 mg KOH/g, still more especially in the rangeof from 1 to 30 mg KOH/g and most especially in the range of from 3 to15 mg KOH/g.

Preferably the non-crosslinkable hyperbranched macromolecule(s) has apolyethylene oxide content of 0 to 50% by weight, most preferably 3 to42% by weight, especially 7 to 38% by weight and most especially 12 to35% by weight.

Preferably the non-crosslinkable hyperbranched macromolecule(s) has aweight average molecular weight (Mw) in the range of from 1500 to 80,000Daltons, more preferably in the range of from 2000 to 70,000 Daltons,most preferably in the range of from 3000 to 60,000 Daltons, andespecially in the range of from 5000 to 50,000 Daltons.

The glass transition temperature of the non-crosslinkable hyperbranchedmacromolecule(s) is preferably in the range of from −75 to +80° C., morepreferably in the range of from −60 to +50° C. and most preferably inthe range of from −50 to +20° C.

The aqueous composition of the invention also includes a polymer(s)dispersed therein which is not a non-crosslinkable oligomer(s) andpreferably has a Mw ≧90,000 Daltons, herein termed a “dispersed polymer”for convenience. Preferably the weight average molecular weight of thedispersed polymer(s) Mw in the aqueous polymer dispersion is in therange of from 90,000 to 6,000,000, more preferably in the range of from150,000 to 2,000,000, and especially in the range of from 250,000 to1,500,000 Daltons. If the dispersed polymer(s) is fully precrosslinkedits Mw will be infinite. Also, in some cases, the synthesis to form thenon-crosslinkable oligomer(s) yields, in addition to the low molecularweight oligomer, an amount of very high molecular weight material. Forthe purposes of this invention, such very high molecular weightmaterial, produced in-situ, is to be considered as a dispersed polymer.

The Mw of the dispersed polymer(s) may be <90,000 Daltons, with theproviso that the solution viscosity of the dispersed polymer(s) is atleast 150 Pa·s as determined from a 80% by weight solids solution of thedispersed polymer(s) in at least one of the solvents selected from thegroup consisting of N-methylpyrrolidone, n-butylglycol and mixturesthereof using a shear rate of 90±5 s⁻¹ and at 50±2° C.

Preferably the solution viscosity (if measurable) of the dispersedpolymer(s) when used in the aqueous composition of the invention is ≧250Pa·s, more preferably ≧500 Pa·s, and especially ≧1000 Pa·s as determinedfrom a 80% by weight solids solution of the dispersed polymer(s) in atleast one of the solvents selected from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof using a shearrate of 90±5 s⁻¹ and at 50±2° C.

The solution viscosity of the dispersed polymer(s) may not be measurableif for example the weight average molecular weight is so high so as torender the dispersed polymer(s) insoluble in organic solvent(s) or ifthe dispersed polymer(s) is fully or partially crosslinked, againrendering it insoluble.

The dispersed polymer(s) may be film forming or non-film forming atambient temperature.

The dispersed polymer(s) may for example be the product of an aqueousemulsion polymerisation or a preformed polymer dispersed in water.

Preferably the dispersed polymer(s) has a measured Tg (using DSC) whichis preferably in the range of from −50 to 300° C., and more preferablyin the range of from 25 to 200° C. and especially in the range of from35 to 125° C. If the dispersed polymer(s) is a vinyl polymer, the vinylpolymer may be a sequential polymer, i.e. the vinyl polymer will havemore than one Tg. Especially preferred is a vinyl polymer with 10 to 50wt. % of a soft part with a Tg in the range of from −30 to 20° C. and 50to 90 wt. % of a hard part of with a Tg in the range of from 60 to 110°C. This combination provides an additional advantage of improved blockresistance of the resultant coating, especially when co-solvent levelsof 0 to 15 wt. %, more preferably 0 to 5 wt. % and most preferably 0 to3 wt. %. of the aqueous composition are used. Blocking is the well-knownphenomenon of coated substrates which are in contact tending tounacceptably adhere to each other, for examples doors and windows intheir respective frames, particularly when under pressure, as forexample in stacked panels.

Preferably the dispersed polymer(s) has an average particle size in therange of from 25 to 1000 nm, more preferably 50 to 600 nm, morepreferably 100 to 500 nm and especially in the range of from 150 to 450nm. The dispersed polymer(s) may also have a polymodal particle sizedistribution.

The dispersed polymer(s) may for example be a vinyl polymer,polyurethane, polyester, polyether, polyamide, polyepoxide, or a mixturethereof. The dispersed polymer(s) may also be a hybrid of two or moredifferent polymer types such as urethane-acrylic polymers (as describedin for example U.S. Pat. No. 5,137,961), epoxy-acrylic polymers andpolyester-acrylic polymers. The dispersed polymer(s) may also be anorganic-inorganic hybrid, for example silica particles grafted with avinyl polymer(s). Preferably the dispersed polymer(s) is a vinylpolymer. Blends of dispersed polymers may of course also be used.

The dispersed polymer(s) may optionally contain acid groups. Thepreferred acid value of the dispersed polymer(s) depends on the type andmolecular weight of non-crosslinkable oligomer(s) and (if present) thetype of cosolvent used. If the non-crosslinkable oligomer(s) ishydrophilic, the cosolvent (if used) is preferably also of a hydrophilicnature and a low acid value of the dispersed polymer(s) is preferred(preferably below 40, more preferably below 30, especially below 24,more especially below 19 and most especially below 15 mg KOH/g). Ifhowever a hydrophobic non-crosslinkable oligomer is used, for instancewithout dispersing groups, the co-solvent is preferentially of ahydrophobic nature (if at all present) and therefore much higher acidvalues (up to an acid value of 160, more preferably up to an acid valueof 125, most preferably up to an acid value of 100 mg KOH/g) of thedispersed polymer(s) may be tolerated to give the desired properties.

The dispersed polymer(s) may optionally contain hydroxyl groups. If thedispersed polymer(s) is a vinyl polymer comprising polymerised(meth)acrylic monomers then preferably the hydroxyl group content in thevinyl polymer is preferably below 1.0 wt. %, more preferably below 0.5wt. % and most preferably below 0.2 wt. % based on the weight of thevinyl polymer.

The dispersed polymer(s) may optionally contain amide groups (suchgroups being e.g. obtainable from amide functional monomers such as(meth)acrylamide). If the dispersed polymer(s) is a vinyl polymercomprising polymerised (meth)acrylamide monomers, then preferably theamide group content in the vinyl polymer is below 3.0 is wt. %, morepreferably below 1.5 wt. % and most preferably below 0.6 wt. % based onthe weight of the vinyl polymer.

The dispersed polymer(s) may optionally contain wet-adhesion promotinggroups such as acetoacetoxy groups, (optionally substituted) amine orurea groups, for example cyclic ureido groups, imidazole groups,pyridine groups, hydrazide or semicarbazide groups.

The dispersed polymer(s) may optionally contain crosslinker groups whichallow crosslinking of the dispersed polymer(s), thus speeding up thedrying rate and improving the properties of the final coating (e.g.chemical resistance and scratch resistance). Examples of suchcrosslinker groups include groups which can take part in autoxidationand groups which will effect crosslinking other than by autoxidation,for example by Schiff base and silane condensation reactions. Thedispersed polymer(s) may crosslink at ambient temperature by a number ofmechanisms including but not limited to autoxidation, Schiff basecrosslinking and silane condensation. By crosslinking by autoxidation ismeant that crosslinking results from an oxidation occurring in thepresence of air and usually involves a free radical mechanism and ispreferably metal-catalysed resulting in covalent crosslinks. By Schiffbase crosslinking is meant that crosslinking takes place by the reactionof a carbonyl functional group(s), where by a carbonyl functional groupherein is meant an aldo or keto group and includes an enolic carbonylgroup such as is found in an acetoacetyl group with a carbonyl-reactiveamine and/or hydrazine (or blocked amine and/or blocked hydrazine)functional group. By silane condensation is meant the reaction of alkoxysilane or —SiOH groups in the presence of water, to give siloxane bondsby the elimination of water and/or alkanols (for example methanol)during the drying of the aqueous coating composition.

Other crosslinking mechanisms known in the art include those provided bythe reaction of epoxy groups with amino, carboxylic acid or mercaptogroups, the reaction of mercapto groups with ethylenically unsaturatedgroups such as fumarate and acryloyl groups, the reaction of maskedepoxy groups with amino or mercapto groups, the reaction ofisothiocyanates with amines, alcohols or hydrazines, the reaction ofamines (for example ethylenediamine or multifunctional amine terminatedpolyalkylene oxides) with β-diketo (for example acetoacetoxy oracetoamide) groups to form enamines. The use of blocked crosslinkergroups may be beneficial. However, crosslinker groups should be chosenwith care so as to not result in any crosslinking of any functionalgroups that may be carried on the non-crosslinkable oligomer(s).

Preferably a significant part of any crosslinking reaction only takesplace after application of the aqueous coating composition to asubstrate, to avoid an excessive molecular weight build up in theinvention composition prior to such application (by precrosslinking)which may lead to impaired film formation and a decrease inwater-resistance.

In an embodiment the dispersed polymer(s) may be fully or partiallypre-crosslinked (i.e. fully or partially crosslinked while present inthe invention aqueous coating composition and prior to applying acoating). Preferably the dispersed polymer(s) is partiallypre-crosslinked. If the dispersed polymer(s) is a dispersed vinylpolymer(s) pre-crosslinking may be achieved by using polyunsaturatedmonomers during the vinyl polymer synthesis such as allyl methacrylate,diallyl phthalate, tripropylene glycol di(meth)acrylate, 1,4-butanedioldiacrylate and trimethylol propane triacrylate. Allyl methacrylate ismost preferred. Alternatively very low levels of initiator may be used,leading to chain-transfer to the dispersed vinyl polymer(s) and hence tografting and high Mw. Other ways to generate pre-crosslinking in adispersed vinyl polymer(s) is to include the use of monomer(s) bearinggroups which may react with each other during synthesis to effectpre-crosslinking for example glycidylmethacrylate and acrylic acid.

Examples of vinyl monomers which may be used to form dispersed vinylpolymer(s) include those described above for forming a non-crosslinkablevinyl oligomer(s).

The vinyl monomer may optionally contain functional groups to contributeto the crosslinking of the vinyl polymer(s) in the coating. Examples ofsuch groups include maleic, epoxy, fumaric, acetoacetoxy, β-diketone,unsaturated fatty acid, acryloyl, methacrylol, styrenic, (meth)allylgroups, mercapto groups, keto or aldehyde groups (such asmethylvinylketone, diacetoneacrylamide and (meth)acroleine).

Particularly preferred dispersed vinyl polymer(s) are acrylic polymer(s)prepared from acrylic monomers as described above.

If the dispersed polymer(s) is a vinyl polymer, the dispersed vinylpolymer may in some embodiments comprise at least 15 wt. %, morepreferably at least 40 wt. % and most preferably at least 60 wt. % ofpolymerised vinyl acetate. If the dispersed vinyl polymer comprises atleast 50 wt. % of polymerised vinylacetate then preferably the dispersedvinyl polymer also comprises 10–49 wt. % of either n-butylacrylate or abranched vinylester, for example VeoVa 10.

In a preferred embodiment the dispersed vinyl polymer(s) comprises:

-   -   I. 15 to 60 wt. % of styrene and/or α-methylstyrene;    -   II. 15 to 80 wt. % of one or more of methyl methacrylate, ethyl        methacrylate, cyclohexyl(meth)acrylate and n-butyl methacrylate;    -   III. 0 to 5 wt. %, more preferably 0 to 3.5 wt. %, of vinyl        monomer(s) containing a carboxylic acid group(s);    -   IV. 0 to 10 wt. %, more preferably 0 to 5 wt. % of vinyl        monomer(s) containing a non-ionic water-dispersing group(s);    -   V. 5 to 40 wt. % of vinyl monomer(s) other than as in I to IV,        VI and VII;    -   VI. 0 to 5 wt. % of vinyl monomer(s) containing wet adhesion        promoter or crosslinker groups (excluding any within the scope        of III and VII); and    -   VII. 0 to 8 wt. %, more preferably 0 to 4 wt. %, and most        preferably 0.5 to 3 wt. % of a polyethylenically unsaturated        vinyl monomer,        wherein I)+II) add up to at least 50 wt. % and        I+II+III+IV+V+VI+VII add up to 100%.

The dispersed polymer(s) can be prepared by any known technique.Preparation techniques particularly include either dispersing apre-formed polymer or polymer solution in water or if the dispersedpolymer(s) is a vinyl polymer directly synthesising the vinyl polymer inwater (for example by emulsion polymerisation, micro-suspensionpolymerisation or mini emulsion polymerisation). Methods for preparingaqueous dispersed polymer(s) are reviewed in the Journal of CoatingTechnology volume 66, number 839, pages 89–105 (1995) and these methodsare included herein by reference. Preferably dispersed vinyl polymer(s)are prepared by the emulsion polymerisation of free radicallypolymerisable olefinically unsaturated monomers (Emulsion Polymerisationand Emulsion Polymers, P. Lovell, M. S. El-Aasser, John Wiley, 1997).Any published variant of the emulsion polymerisation process may beutilised to prepare the dispersed polymer(s), including the use ofseeded emulsion polymerisation techniques to control particle size andparticle size distribution, especially when working in the particle sizerange 300–700 nm when the seeded technique is useful for giving goodparticle size control. Other useful techniques are the so calledsequential polymerisation technique and the power feed technique(chapter 23 in “Emulsion Polymers and Emulsion Polymerisation” D RBasset and A E Hamielec, ACS Symposium Series No 165, 1981).

Preferably the dispersed polymer(s) is colloid stable and it is alsodesirable that colloid stability is maintained for as long as possibleinto the drying process since early loss of colloid stability can bringa premature end to open time. Since the final coating composition mayoften contain co-solvents and dissolved ionic species (e.g. from pigmentdissolution and from the presence of neutralising agents), it isdesirable that the colloid stability of the dispersed polymer(s) isadequate to withstand any destabilising influences of these components.Colloid stability may be achieved by the addition of conventionalnon-ionic surfactants, optionally with the addition of anionicsurfactants at any stage during the preparation of the aqueouscomposition of the invention. Strongly adsorbing surfactants capable ofproviding steric stability are preferred. Higher levels of colloidstability may be obtained by chemically binding or partially bindinghydrophilic stabilising groups such as polyethylene oxide groups to thesurface of dispersed polymer(s) particles. Suitable surfactants andstabilising groups are described in “Non Ionic Surfactants-PhysicalChemistry” (M J Schick, M Dekker Inc. 1987) and “Polymer Colloids”(Buscall, Corner & Stageman, Elsevier Applied Science Publishers 1985).

Chemical binding (grafting) of hydrophilic stabilising groups ontodispersed polymer(s) particles can be achieved by the use of acomonomer, polymerisation initiator and/or chain transfer agent bearingthe stabilising group, for example methoxy(polyethylene oxide)₃₀methacrylate may be introduced as a comonomer into an emulsionpolymerisation to give rise to stabilised dispersed polymer particleswith bound polyethylene oxide groups on the particle surface. Anothermethod of producing a strongly sterically stabilised dispersedpolymer(s) is to introduce cellulosic derivatives (e.g. hydroxy ethylcellulose) during an emulsion polymerisation (see for example D H Craig,Journal of Coatings Technology 61, no. 779, 48, 1989). Hydrophilicstabilising groups may also be introduced into a preformed polymerbefore it is subsequently dispersed in water, as described in EP 0317258where polyethylene oxide groups are reacted into a polyurethane polymerwhich is subsequently dispersed in water and then chain extended.

The combination of non-crosslinkable oligomer(s) and dispersedpolymer(s) is most conveniently prepared by physically blending thecorresponding aqueous dispersions. However other methods of preparingthe combination can sometimes be utilised. One such method is to preparethe non-crosslinkable oligomer(s) in organic solvent solution aspreviously discussed, and to disperse this solution directly into anaqueous dispersed polymer(s). Alternatively the organic solvent can beremoved from the non-crosslinkable oligomer(s) solution, and thenon-crosslinkable oligomer(s) directly dispersed into an aqueousdispersed polymer(s). The dispersed polymer(s) can also be added to anorganic solvent solution of the non-crosslinkable oligomer(s). Anothermethod is to introduce the non-crosslinkable oligomer(s) into an aqueousfree radical polymerisation reaction which produces the dispersedpolymer(s). Such an introduction of non-crosslinkable oligomer(s) may beat the commencement of the aqueous free radical polymerisation and/orduring the aqueous free radical polymerisation. (Also, as mentionedpreviously, a dispersed polymer(s) can sometimes be formed in-situ fromthe synthesis of a oligomer as a very high molecular weight polymerfraction resulting from the oligomer synthesis).

The non-crosslinkable oligomer(s) may also be diluted with reactivediluent (for example vinyl monomers) at any stage of its preparation andthen dispersed in water containing a dispersed polymer(s), followed bypolymerisation of the reactive diluent in the presence of the noncrosslinkable oligomer(s) and the dispersed polymer(s). Optionally,depending on the nature of the reactive diluent, no furtherpolymerisation of the reactive diluent prior to use in a coating may berequired.

Alternatively the non-crosslinkable oligomer(s) and dispersed polymer(s)may be combined by preparing a redispersible dry powder form of thedispersed polymer(s), and then dispersing the redispersible dry powderdirectly into an aqueous dispersion of the non-crosslinkableoligomer(s). Methods for preparing redispersible dry powders frompolymer emulsions are described for example in U.S. Pat. No. 5,962,554,DE 3323804 and EP 0398576.

In a preferred embodiment of the invention the non-crosslinkableoligomer(s) and the dispersed polymer(s) are compatible in the dryingaqueous composition. Preferably the non-crosslinkable oligomer(s) andthe dispersed polymer(s) give clear films upon film formation aftercoating of the aqueous composition onto a substrate.

Preferably the ratios by weight of solid material of non-crosslinkableoligomer(s) to dispersed polymer(s) i.e. a):b), are in the range of from8:92 to 50:50, more preferably in the range of from 10:90 to 40:60,still more preferably in the range of from 15:85 to 30:70 and mostpreferably in the range of from 25:75 to 50:50.

The aqueous coating compositions of the invention are particularlyuseful when in the form of final coating formulations (i.e. compositionintended for application to a substrate without any further treatment oradditions thereto) such as protective or decorative coating compositions(for example paint, lacquer or varnish) wherein an initially preparedcomposition may be further diluted with water and/or organic solventsand/or combined with further ingredients, or may be in more concentratedform by optional evaporation of water and/or organic components of theliquid medium of an initially prepared composition.

Preferably the evaporation rate of any co-solvent used is ≦0.6, morepreferably ≦0.15, most preferably ≦0.08 and especially ≦0.035. Valuesfor evaporation rates were published by Texaco Chemical Company in abulletin Solvent Data: Solvent Properties (1990). (The values given arerelative to the evaporation rate (ER) is defined as 1.00). Determinationof evaporation rates of solvents that are not listed the Texaco bulletinis as described in ASTM D3539.

In a special embodiment, the amount of co-solvent(s) used in theinvention composition is preferably linked to the Mw of thenon-crosslinkable oligomer(s) in the composition. For anon-crosslinkable oligomer(s) with Mw in the range 1,000 to 40,000Daltons, the amount of co-solvent, i.e. c), is preferably 0 to 15 wt. %based on the weight of the composition, more preferably 0 to 10 wt. %.For a non-crosslinkable oligomer(s) with Mw in the range of from 40,000to 80,000 Daltons, the corresponding figures for the preferred amount ofco-solvent are 0 to 18 wt. %, more preferably 5 to 18 wt. %.

Furthermore, there is also a preferred relationship between the amountof co-solvent used and the amount of binder polymer solids(non-crosslinkable oligomer plus dispersed polymer), the amount ofco-solvent is preferably ≦50 wt % based on the weight of binder polymersolids in the composition, more preferably ≦35 wt %, more preferably ≦20wt %, more preferably ≦10 wt %, and especially preferably 0 wt % withthe proviso that the amount of co-solvent is 0 to 20 wt % of thecomposition.

An advantage of the present invention is that (if used) co-solvent can;if as is often required for environmental and safety reasons, be presentat very low concentrations because of the plasticising nature of thenon-crosslinkable oligomer(s). Preferably the co-solvent to water ratiois below 0.8, more preferably below 0.4, most preferably below 0.2 andespecially below 0.1. The co-solvent(s) can all be added at the finalformulation step. Alternatively some or all of the co-solvent in thefinal formulation can be the co-solvent utilised in the preparation ofthe non-crosslinkable oligomer(s). An important consideration whenchoosing a co-solvent is whether or not the co-solvent is compatiblewith the non-crosslinkable oligomer(s) and/or the dispersed polymer(s)and the effect of any co-solvent partitioning (and the partitioning ofthe co-solvent in the (aqueous) oligomer phase versus the dispersedpolymer particles is preferably >1/1, more preferably >2/1 and mostpreferably >3/1). If the co-solvent is more compatible with thedispersed polymer(s) it will swell the dispersed polymer, thusincreasing the overall viscosity. Preferably any co-solvent present inthe aqueous composition of the invention is more compatible with thenon-crosslinkable oligomer(s) then with the dispersed polymer(s), sothat the dispersed polymer(s) undergoes little if any swelling by theco-solvent. The co-solvent selection is often determined byexperimentation and/or by the use of a solubility parameter concept i.e.maximising the difference in the solubility parameter of the dispersedpolymer(s) and solvent leads to a minimisation of the co-solvent uptakeby the dispersed polymer(s). Solubility parameters of a range ofsolvents and a group contribution method for assessing the solubilityparameters of polymers are given by E A Grulke in the “Polymer Handbook”(John Wiley pages 519–559, 1989) and by D W Van Krevelen and P JHoftyzer in “Properties of Polymers. Correlations With ChemicalStructure” (Elsevier, New York, 1972 chapters 6 and 8). Co-solventuptake of the dispersed polymer(s) may also be decreased by increasingits Tg so that the dispersed polymer(s) is in the glassy region atambient temperature, or by pre-crosslinking the dispersed polymer(s) asdescribed above.

The aqueous coating composition of the invention may be applied to avariety of substrates including wood, board, metals, stone, concrete,glass, cloth, leather, paper, plastics, foam and the like, by anyconventional method including brushing, dipping, flow coating, spraying,and the like. They are, however, particularly useful for providingcoatings on wood and board substrates. The aqueous carrier medium isremoved by natural drying or accelerated drying (by applying heat) toform a coating.

Accordingly, in a further embodiment of the invention there is provideda coating obtainable from an aqueous coating composition of the presentinvention.

The aqueous coating composition of the invention may contain otherconventional ingredients, some of which have been mentioned above;examples include pigments (especially inorganic pigments), dyes,emulsifiers, surfactants, plasticisers, thickeners, heat stabilisers,levelling agents, anti-cratering agents, fillers, sedimentationinhibitors, UV absorbers, antioxidants, dispersants, flow agents,adhesion promoters, defoamers, co-solvents, wetting agents; oligomersand polymers (crosslinkable and/or non-crosslinkable) which are notaccording to the invention such as may be used in conventional bindersystems; and the like introduced at any stage of the production processor subsequently. Preferably the composition of the invention comprises 0to 50 wt %, more preferably 0 to 40 wt %, most preferably 0 to 35 wt %,especially 0 to 30 wt %, more especially 0 to 25 wt % and mostespecially 5 to 25 wt % of pigment(s). It is possible to include anamount of antimony oxide in the dispersions to enhance the fireretardant properties. Optionally external crosslinking agent(s) may beadded to the aqueous composition of the invention to aid crosslinking ofthe dispersed polymer(s) during and after drying.

In particular, the aqueous coating compositions of the invention, if thedispersed polymer(s) is autoxidisable, advantageously include a driersalt(s). Drier salts are well known to the art for further improvingcuring in unsaturated film-forming substances. Generally speaking, driersalts are metallic soaps, that is salts of metals and long chaincarboxylic acids. It is thought that the metallic ions effect the curingaction in the film coating and the fatty acid components confercompatibility in the coating medium. Examples of drier metals arecobalt, manganese, zirconium, lead, neodymium, lanthanum and calcium.The level of drier salt(s) in the composition is typically that toprovide an amount of metal(s) within the range of from 0.01 to 0.5% byweight based on the weight of autoxidisable dispersed polymer(s).

Drier salts are conventionally supplied as solutions in white spirit foruse in solvent-borne alkyd systems. They may, however, be used quitesatisfactorily in aqueous coating compositions since they can normallybe dispersed in such systems fairly easily. The drier salt(s) may beincorporated into the aqueous coating composition at any convenientstage. Drier accelerators may be added to the drier salts. Suitabledrier accelerators include 2,2′-bipyridyl and 1,10-phenanthroline.

FIGS. 1 to 4 illustrate the drying profile of a composition according tothe present invention [Example 3], where the equilibrium viscosity ismeasured as the solids content increases.

FIG. 1 shows the drying profile measured using a shear rate of 0.1 s⁻¹.

FIG. 2 shows the drying profile measured using a shear rate of 1.0 s⁻¹.

FIG. 3 shows the drying profile measured using a shear rate of 10.0 s⁻¹.

FIG. 4 shows the drying profile measured using a shear rate of 77.9 s⁻¹.

The present invention is now illustrated by reference to the followingexamples. Unless otherwise specified, all parts, percentages and ratiosare on a weight basis.

Test Methods:

To test for the open time and wet edge time of the aqueous compositionsprepared as described in the examples below, the aqueous composition wasapplied using a wire rod to a test chart (18×24 cm, form 8B-display,available from Leneta Company) at a wet film thickness of 120 μm. Opentime and wet edge time tests were performed at fairly regular timeintervals according to the approximate expected final times in each case(being determined roughly from a trial run), the intervals betweenmeasurements decreasing towards the end of the run. The measurementswere carried out at relative humidity levels of 50+/−5%, temperatures of23+/−2° C. and an air flow ≦0.1 m/s.

Open Time:

The open time was determined by brushing at regular time intervals (asmentioned above) a virgin 75 cm² area of the coated chart with a brush(Monoblock no 12, pure bristles/polyester 5408-12) carrying some more ofthe composition with a brush pressure of 100 to 150 g during 30 seconds.In this time the brush was moved in one set comprising 5 times in thedirection of the width of the substrate and 5 times in the direction oflength of the substrate before visually assessing the coating. Once thecomposition carried on the brush no longer formed a homogeneous layerwith the coating on the substrate the open time was considered to beover.

Wet Edge Time:

The wet edge time was determined by brushing at regular time intervals(as mentioned above) a virgin 25 cm² edge area of the coated chart witha brush (Monoblock no 12, pure bristles/polyester 5408-12) carrying somemore of the composition with a brush pressure of 100 to 150 g during 30seconds. In this time the brush was moved in one set comprising 5 timesin the direction of the width of the substrate and 5 times in thedirection of length of the substrate before visually assessing thecoating. Once the composition carried on the brush no longer formed ahomogeneous layer with the coating on the substrate and/or a visible lapline could be seen the wet edge time was considered to be over.

Drying Time:

To test the dust-free, tack-free and thumb-hard drying stages of theaqueous compositions prepared in the examples as described below, theaqueous composition was applied to a glass plate at a wet film thicknessof 80 μm. Drying time tests were performed at regular time intervals atrelative humidity levels of 50+/−5%, temperatures of 23+/−2° C. and anair flow ≦0.1 m/s.

Dust-Free Time:

The dust-free time was determined by dropping a piece of cotton wool(about 1 cm³ i.e. 0.1 g) onto the drying film from a distance of 25 cm.If a person could immediately blow the piece of cotton wool from thesubstrate without leaving any wool or marks in or on the film, the filmwas considered to be dust-free.

Tack-Free Time:

The tack-free time was determined by placing a piece of cotton wool(about 1 cm³, 0.1 g) on the drying film and placing a metal plate (witha diameter of 2 cm) and then a weight of 1 kg onto the piece of cottonwool (for 10 seconds). If the piece of cotton wool could be removed fromthe substrate by hand without leaving any wool or marks in or on thefilm, the film was considered to be tack-free.

Thumb-Hard Time:

The thumb-hard time was determined by placing the coated glass plate ona balance and a thumb was pressed on the substrate with a pressure of 7kg. The thumb was then rotated 90° under this pressure. If the film wasnot damaged the coating was dried down to the substrate level andconsidered to be thumb-hard.

Sandability

Sandability corresponds to the hardness of a coating at the point when acoating can be sanded properly. The composition prepared in the Examplesdescribed below was applied to a piece of wood at a wet film thicknessof 120 μm. The coating was abraded by hand with sandpaper (graindelicacy P150) at regular time intervals at relative humidity levels of50+/−5%, temperatures of 23+/−2° C. and an air flow ≦0.1 m/s. When therewas no significant clogging (or the coating started powdering) thecoating was considered to be sandable.

Viscosity:

All viscosity measurements were performed on a TA Instruments AR2000NRheometer, using cone & plate and/or plate & plate geometries, dependingon the viscosity of the sample to be measured. A Peltier heating/coolingunit in the bottom plate was used to control the temperature.

Solution Viscosity

For the solution viscosity measurements (both at 50±2° C. and at 23±2°C.), a cone & plate (4 cm diameter, 10 angle, gap 29 μm) was used. Ifthe oligomer solutions were too low in viscosity to remain in betweenthe cone and the plate, the cup & spindle C14 geometry was used and theviscosity measurements were performed at a shear rate of 91.9 s⁻¹. Forboth geometries, the gap between the cone and the plate (or between thecup and the spindle) was set to 0.1 mm, prior to each measurement. Thesolution viscosities of the non-crosslinkable oligomers were measuredusing the solvent systems and the conditions as defined herein in thestatements of invention:

-   1. The 80% solids solution: The non-crosslinkable oligomer was    diluted (if necessary) with the appropriate solvent to an 80% solids    solution (in NMP, BG or a mixture of NMP and BG at any ratio) which    was homogenised by stirring the solution for 15 minutes at 50° C.-   2. The 70% solids solution: The non-crosslinkable oligomer was    diluted with the appropriate solvent (or mixture of solvents) to    result in a 70% solids solution (either in NMP/water/DMEA or in    BG/water/DMEA, or in (a mixture of NMP and BG at any    ratio)/water/DMEA; for each solvent mixture the solvents should be    present in a weight ratio of 2017/3, respectively) which was    homogenised by stirring the solution for 15 minutes at 50° C. The    resulting solution was subsequently cooled.

The solution viscosity of the oligomer was measured at a temperature of50±2° C. for the 80% solids oligomer solution and at 23±2° C. for the70% solids oligomer solution at a shear rate of 90±5 s⁻¹.

Equilibrium Viscosity

The equilibrium viscosity measurements were performed with a plate &plate (diameter 15 mm, gap 500 μm, at 23±0.1° C.). All compositionsdescribed in the examples below were used at the solids level at whichthey were prepared and not diluted to lower solids levels.

Step 1: Three test charts were provided with coatings of identical filmthickness. The coatings were applied with a 120 μm wire rod and theactual film thickness (and its uniformity) was checked with a wet filmgauge, 20 to 370 μm, of Braive Instruments. The charts were dried underidentical conditions in an environment where the air flow was <0.1 m/s.

Step 2: One test chart was used to determine the solids increase intime. The weight of the film was monitored in time, starting right afterapplication of the film. After calculating the solids content at everymeasurement, a solids-time curve could be constructed and a trend linewas calculated for the solids of the film as a function of the dryingtime.

Step 3: The other two test charts were used to determine the equilibriumviscosity in time: approximately every 5 minutes a sample was scrapedfrom one test chart (in random order) and the viscosity of this samplewas measured at 23° C. at representative shear rates, for example at 0.1s⁻¹, 1 s⁻¹, 10 s⁻¹ and 77.9 s⁻¹. The measurements were continued for 90minutes, unless reproducible sampling from the test charts could not beperformed properly within that period of time (due to for example dryingof the film to reach the dust free time).

Step 4: The final drying curve of the coating as shown in FIGS. 1 to 4(in which the equilibrium viscosity is represented as a function of thesolids of the drying film) could be constructed from the solids-timecurve (Step 2) and the equilibrium viscosity data (Step 3).

Molecular Weight Determination

Gel permeation chromatography (GPC) analyses for the determination ofpolymer molecular weights were performed on an Alliance Waters 2690 GPCwith two consecutive PL-gel columns (type Mixed-C, I/d=300/7.5 mm) usingtetrahydrofuran (THF) as the eluent at 1 cm³/min and using an AllianceWaters 2410 refractive index detector. Samples corresponding to about 16mg of solid material were dissolved in 8 cm³ of THF, and the mixtureswere stirred until the samples had dissolved. The samples were leftundisturbed for at least 24 hours for complete “uncoiling” andsubsequently were filtered (Gelman Acrodisc 13 or 25 mm ø CR PTFE; 0.45μm) and placed on the auto-sampling unit of the GPC. A set ofpolystyrene standards (analysed according to DIN 55672) was used tocalibrate the GPC.

All species with a molecular weight less than 1000 Daltons are ignoredwhen calculating the Mw and PDi for the non-crosslinkable oligomers.When Daltons are used in this application to give molecular weight data(g/mole), it should be understood that this is not a true molecularweight, but a molecular weight measured against polystyrene standards asdescribed above.

Water Solubility

The water solubility of non-crosslinkable oligomer(s) was determined asfollows: A sample of a non-crosslinkable oligomer was dispersed in waterand diluted with water/ammonia to 10% solids and the pH adjusted to thedesired pH, within a range of from 2 to 10, and the dispersion was thencentrifuged over 5 hours at 21000 rpm at 23±2° C. on a Sigma 3K30centrifuge (21,000 rpm corresponds to a centrifugal force of 40,000 g).The pH chosen should be the pH where the non-crosslinkable oligomer isexpected to be most soluble, for example often a pH of about 9 issuitable for anionic stabilised dispersions and a pH of about 2 is oftensuitable for cationic stabilised dispersions. After centrifugation asample of the supernatant liquid was taken and evaporated for 1 hour at150° C. to determine the solids content of the supernatant liquid. Thewater-solubility percentage was calculated by dividing the amount ofsolids (g) of the supernatant by the total of amount of solids in thesample and multiplying by 100.

Surface Hardness

König hardness was determined following DIN 53157 NEN5319 using Erichsenhardness measuring equipment. The values are given in second(s) and thehigher the value is the harder the coating is.

Water Resistance

The examples prepared as described below were cast down on Leneta testcharts Form 2C with a wet film thickness of 100 μm. The films were driedat room temperature for 20 minutes and at 50° C. for 16 hours. Afterthey were cooled down to room temperature the films were tested forwater resistance.

A drop of water was placed on the films and covered with a watch glass.The water was removed after 4 hours at room temperature and the damageto the coating was assessed. 0 means that the coating was dissolved, 5means that the coating was not affected at all.

Materials & Abbreviations used: MPEG750 = methoxy polyethylene glycol(Mn ≈ 750) MPEG350MA = methoxy polyethylene glycol (Mn ≈ 350)methacrylate available from LaPorte DMPA = dimethylol propionic acid NMP= N-methyl pyrrolidone TDI = toluene diisocyanate Dowanol DPM =dipropylene glycol monomethyl ether Atlas G5000 = ethoxylated surfactantavailable from Uniqema Boltorn H20 = dendritic polymer available fromPerstorp Atpol E5720/20 = fatty alcohol ethoxylate available fromUniqema AP = ammonium persulphate Aerosol OT-75 = sodium dioctylsulphosuccinate available from Cytec MMA = methyl methacrylate n-BA =n-butyl acrylate AA = acrylic acid SLS = sodium lauryl sulphateBorax.10H₂O = disodium tetraborate decahydrate Akyposal NAF = sodiumdodecyl benzene sulphonate available from KAO Chemicals Natrosol 250LR =hydroxy ethyl cellulose available from Hercules Akyporox OP-250V = octylphenol ethoxylate available from KAO Chemicals VeoVa 10 = vinyl ester ofversatic acid available from Shell Water = demineralised water DMEA =N,N-dimethyl ethanolamine Voranol P400 = polypropylene glycol availablefrom Now Chemical.Preparation of a Non-Crosslinkable Urethane Oligomer: A1

A 1 liter flask, equipped with a stirrer and a thermometer, was loadedwith DMPA (48.09), NMP (240.0 g), MPEG750 (19.2 g) and Voranol P400(618.64 g) in a nitrogen atmosphere. The reaction mixture was stirreduntil a clear solution was obtained. At a maximum temperature of 25° C.,TDI (274.46 g) was fed into this reaction mixture without exceeding areactor temperature of 50° C. After the TDI-feed was complete, thereaction mixture was heated to 80° C. and stirred at this temperaturefor 1 hour after which the NCO-free urethane oligomer A1 was obtained.

Preparation of a Non-Crosslinkable Urethane Oligomer Dispersion: DA1

At a temperature of 70° C., the alkyd urethane oligomer A1 was dilutedwith Dowanol DPM (123.34). Subsequently DMEA (32.24) was added and themixture was stirred for 15 minutes. Then water (373.12 g) was added andthe temperature was lowered to 55 to 60° C. The resultant predispersionwas stirred for an additional 15 minutes. Part of the resultantpredispersion (1100 g), at 55 to 60° C., was dispersed in water (736.7g; 45 to 50° C.), over 60 minutes and under a nitrogen atmosphere. Afterthe addition was complete, the final dispersion was stirred for anadditional 15 minutes, cooled to ambient temperature, filtered over a200-mesh sieve and stored under nitrogen. The dispersion DA1 had asolids content of 30.7 wt % and a pH of 7.04.

Preparation of a Non-Crosslinkable Hyperbranched Polyester AmideOligomer: A2

A 2 liter flask fitted with a stirrer, a thermometer and a condenserfitted with a Dean-Stark condensate trap, was loaded with diisopropanolamine (297.15 g) in a nitrogen atmosphere. Stirring was started andhexahydrophthalic anhydride (309.56 g) was added in one portion. Thiscaused an exothermic reaction and the temperature rose to 140° C. Thenlauric acid (393.29 g) was added and the reaction mixture was heated to180° C. The mixture was kept at 180° C. and water was collected until anacid value of 3.8 mg KOH/g was obtained. The reaction mixture wasallowed to cool to 100° C. and then succinic anhydride (41.35 g) wasadded. The resulting reaction mixture was heated to 120° C., and wasstirred at this temperature until all the anhydride had reacted, asjudged from an Infra Red spectrum of the reaction mixture.

Preparation of a Non-Crosslinkable Hyperbranched Polyester AmideOligomer Dispersion: DA2

At 70° C., a portion of the hyperbranched polyester amide A2 (195.22 g)was diluted with Dowanol DPM (77.78 g) and DMEA (8.47 g) wassubsequently added. The resultant solution was dispersed in water by theaddition of hot water (50° C., 368.53 g) over a period of 10 minutes.The resulting dispersion DA2 was stirred for an additional 30 minutes at50° C. and subsequently cooled to ambient temperature, filtered andstored in a nitrogen atmosphere. The dispersion DA2 had a solids contentof 30.0 wt %.

Preparation of a Non-Crosslinkable Vinyl Oligomer Dispersion: DA3

A 2 liter flask, equipped with stirrer and condenser, was charged with47 parts of demineralised water and 0.18 parts of a 30 wt % solution ofSLS in water. The mixture was heated up to 70° C. at which point 10 wt %of a monomer feed consisting of 12 parts of demineralised water, 0.55parts of a 30 wt % solution of SLS in water, 0.69 parts of laurylmercaptane, 2.89 parts of MPEG350MA, 23.14 parts of n-BA, and 2.89 partsof MMA was added. The mixture was further heated to 75° C. and 21.99parts of a 1.77 wt % solution of AP in water was added. The batch wasthen heated to 85° C. As soon as the polymerisation temperature wasreached the remainder of the monomer feed was added over a period of 120minutes and 51.4 parts of a 1.77 wt % solution of AP in water was addedover a period of 130 minutes. At the end of the monomer feed the feedtank was rinsed with 5 parts of demineralised water and the temperatureof 85° C. was maintained for 20 minutes. Next, enough of a solution of0.095 parts of dimethyl ethanol amine in 0.038 parts of demineralisedwater was added to the flask to reach a pH of 7.5. The temperature of85° C. was maintained for another 20 minutes after which the batch wascooled to 60° C. At that point 0.096 parts of a 30 wt % solution oft-butyl hydroperoxide in water was added to the flask followed by 0.578parts of a 5 wt % solution of isoascorbic acid in water. The batch wasstirred for another 30 minutes before it was cooled to room temperature.0.289 parts of Proxel Ultra 10 was added as a bacteriocide and theemulsion was filtered.

The final dispersion DA3 had a solids content of 30 wt % and a particlesize of 120 nm.

Preparation of a Non-Crosslinkable Polyester Ether Oligomer: A4

A 1 liter flask fitted with a stirrer, a thermometer and a condenserfitted with a Dean-Stark condensate trap, was loaded with polypropyleneglycol (PPG-2000; 350.00 g) and lauric acid (61.54 g) in a nitrogenatmosphere. Stirring was started and the reaction mixture was heated to230° C. The mixture was kept at 230° C. and water was collected until anacid value of <5 mg KOH/g was obtained. The reaction mixture was thenallowed to cool to room temperature and collected.

Preparation of a Non-Crosslinkable Polyester Ether Oligomer DispersionDA4

In a 500 cm³ flask, a portion of the polyester ether A4 (30.0 g) wasmixed with ATLAS G5000 (1.5 g), Dowanol DPM (12.0 g) and DMEA (0.06 g)and the mixture was stirred at 50° C. until a clear solution wasobtained. Then hot water (61.4 g; 50° C.) was added to the flask and theresulting dispersion was stirred at 50° C. for an additional 30 minutes.After cooling to room temperature, the product dispersion was filteredand collected as a translucent dispersion DA4 with a solids content of30.0 wt %.

Preparation of a Non-Crosslinkable Polyester Oligomer: A5

A 1 liter flask fitted with a stirrer, a thermometer and a condenserfitted with a Dean-Stark condensate trap, was loaded with a reactionmixture containing DMPA (44.7 g), adipic acid (194.7 g) and butanediol(135.09). The mixture was heated to 180° C. while stirring and thereaction water was collected by destillation. The reaction mixture wasstirred at 180° C. until an acid value around 40 mg KOH/g was obtained.Then the mixture was cooled to room temperature and collected. Theproduct polyester oligomer A5, which slowly solidified after prolongedstanding at room temperature, had a final acid value of 40.2 mg KOH/g.

Preparation of a Non-Crosslinkable Polyester Oligomer Dispersion: DA5

In a 500 cm³ flask, a portion of the polyester A6 (150.0 g) was mixedwith Dowanol DPM (60.0 g) and DMEA (9.59 g) and the mixture was stirredat 50° C. until a clear solution was obtained. Then hot water (280.41 g;50° C.) was added to the flask and the resulting dispersion was stirredat 50° C. for an additional 30 minutes. The final dispersion DA5 had asolids content of 30.0 wt %.

Preparation of a Non-Crosslinkable Hyperbranched Polyester MacromoleculeA6

A 2 liter flask, equipped with stirrer, was loaded with MPEG750 (1323.53g) and succinic anhydride (176.47 g) in a nitrogen atmosphere. Thereaction mixture was heated to 120° C., and was stirred at thistemperature until all the anhydride had reacted, as judged from an InfraRed spectrum of the reaction mixture (the anhydride groups typicallyshow two absorptions at 1785 cm⁻¹ and 1865 cm⁻¹, which disappeared andwere replaced by a new ester carbonyl absorption at 1740 cm⁻¹). Theclear liquid product was then cooled to 50° C. and collected. Theproduct solidified when left undisturbed at ambient temperature.

A separate 2 liter flask fitted with a stirrer, a thermometer and acondenser fitted with a Dean-Stark condensate trap, was loaded withBoltorn H20 (Trademark from Perstorp AB; 189.38 g), the MPEG750/SANadduct as prepared above (273.92 g), lauric acid (236.70 g) andphosphoric acid (0.5 g) in a nitrogen atmosphere. The reaction mixturewas heated to 220° C. and water was collected until an acid value of 4.9mg KOH/g was obtained.

Preparation of a Non-Crosslinkable Hyperbranched MacromoleculeDispersion DA6

At 70° C., a portion of the hyperbranched polyester A6 (199.18 g) wasdiluted with Dowanol DPM (39.84 g) and NMP (39.84 g) and DMEA (1.14 g)was subsequently added. The resultant solution was dispersed in water bythe addition of hot water (50° C.; 383.94 g) over a period of 10 minutesto the stirred solution of the hyperbranched oligomer. The resultingdispersion DA6 was stirred for an additional 30 minutes at 50° C. andsubsequently cooled to ambient temperature and stored in a nitrogenatmosphere. The dispersion DA6 had a solids content of 30.0 wt %.

The properties (acid values, Mw, PDi and solution viscosities) of theoligomers A1 to A6 are given below in Table 1.

TABLE 1 Oligomers A1 A2 A3 A4 A5 A6 Acid value 20.9 24.3 0 1.3 40.2 4.9mg KOH/g) Solution 87.5 8.8 1.1 0.04 0.10 0.42 viscosity (a) (Pa · s)Solution 72.8 92.6 3.5 0.14 0.21 1.74 viscosity (b) (Pa · s) Mw(Daltons) 15,500 23,400 23,000 3,870 4200 37000 PDi 1.82 7.1 2.1 1.2 2.310.3 Water solubility 100 77.9 0.8 3.1 68.2 64.8 Tg (° C.) 5 11 −52 not−54 & −38 −52 measured measurable Key: (a) = oligomer solution (80%) inNMP (A1, A2, A4, A5, A6) or BG (A3) at 50° C., shear rate 90 s⁻¹ (A1),91.9 s⁻¹ (A2), 92.5 s⁻¹ (A3), 91.9 s⁻¹ (A4 to A6). (b) = oligomersolution (70%) in NMP/Water/DMEA (20/7/3) (A1, A2, A4, A5, A6) orBG/Water/DMEA (20/7/3) (A3) at 23° C., shear rate 90 s⁻¹ (A1), 91.9 s⁻¹(A2), 92.5 s⁻¹ (A3), 91.9 s⁻¹ (A4 to A6).Preparation of Dispersed Vinyl Polymer P1

A 2 liter reactor, equipped with stirrer, thermometer and vortexbreakers, was loaded with demineralised water (652.57 g), Atpol E5720/20(4.99 g) and Borax.10H₂O (3.57 g) in a nitrogen atmosphere. The mixturewas heated whilst stirring to 80° C. and then a solution of AP (2.31 g)in demineralised water (16.00 g) was added. In a dropping funnel apre-emulsion was prepared by stirring a mixture of demineralised water(161.87 g), Atpol E5720/20 (94.85 g), Aerosol OT-75 (7.20 g),Borax.10H₂O (1.07 g), MMA (534.18 g), n-BA (444.32 g) and M (19.97 g).5% of this pre-emulsion was added to the reactor at 80° C. over 5minutes. The remainder was fed into the reactor over 160 minutes at 85°C. A solution of AP (0.53 g) in demineralised water (7.88 g) was addedto the reactor during the first 15 minutes of feeding the pre-emulsifiedfeed. Then the reactor content was kept at 85° C. for 30 minutes, andthen cooled to ambient temperature. The pH was adjusted to 8 to 8.5 with12.5% aqueous ammonia. The resultant dispersed product (P1) was filteredand collected.

Dispersed Urethane Polymer P2 (NeoRez R-2001)

This is a high molecular weight alkyd urethane dispersion obtainablefrom Avecia BV, The Netherlands. NeoRez is a trademark of Avecia.

Preparation of Dispersed Vinyl Polymer P3

A 2 liter reactor, equipped with stirrer, thermometer and vortexbreakers, was loaded with demineralised water (194.509), Akyposal NAF(3.00 g), Borax.10H₂O (1.25 g), acetic acid (0.50 g) and Natrosol 250LR(10.00 g) in a nitrogen atmosphere. The mixture was heated whilststirring to 60° C. and then a solution of AP (0.50 g) in demineralisedwater (10.00 g) was added. In a dropping funnel a pre-emulsion wasprepared by stirring with demineralised water (171.71 g), Akyposal NAF(3.00), Borax.10H₂O (1.25 g), acetic acid (0.50 g) and Akyporox OP-250V(14.29 g) followed by VeoVa 10 (125.00 g) and vinyl acetate (375.00 g).10% of this mixture was added to the reactor at 60° C. The mixture washeated whilst stirring to 80° C. The remainder was fed into the reactorover 90 minutes at 80° C. The content of a separate dropping funnel,containing a solution of AP (1.15 g) in demineralised water (60.00 g),was added in the same time. Then the reactor content was kept at thistemperature for 120 minutes and then cooled to ambient temperature. ThepH was adjusted to 8 to 8.5 with 12.5% aqueous ammonia. The resultantproduct P3 was filtered and collected.

Preparation of a Sequential Dispersed Vinyl Polymer P4

A 2 liter reactor, equipped with stirrer, thermometer and vortexbreakers, was loaded with demineralised water (990.94 g), SLS (30%, 0.55g) and NaHCO₃, (4.44 g) in a nitrogen atmosphere. The mixture was heatedwhilst stirring to 80° C. and then a solution of AP (0.89 g) indemineralised water (5.00 g) was added. In a dropping funnel a monomermixture was prepared by stirring MMA (140.48 g), n-BA (207.71 g) and M(7.11 g). 10% of this mixture was added to the reactor at 80° C. Theremainder was fed into the reactor over a period of 40 minutes at 85° C.The content of a separate dropping funnel, containing demineralisedwater (20.00 g), AP (0.36 g) and SLS 30% (11.62 g) was added in the sametime. The reactor content was kept at 85° C. for 30 minutes. A secondmonomer mixture was prepared in a dropping funnel consisting MMA (464.91g), n-BA (57.37 g) and AA (10.66 g). The mixture was fed to the reactorafter the 30 minutes period in 60 minutes. The content of a separatedropping funnel, containing demineralised water (30.00 g), AP (0.53 g)and SLS 30% (17.44 g) was added in the same time. The reactor contentwas kept at 85° C. for 45 minutes and then cooled to ambienttemperature. The pH was adjusted to 8 to 8.5 with 12.5% aqueous ammonia.The resultant product P4 was filtered and collected.

The properties of P1 to P4 are given in Table 2 below.

TABLE 2 Polymer P1 P2 P3 P4 Solids [wt %] 51.2 35.0 50.3 45.1 pH 8.3 7.78.2 8.3 Particle size [nm] 450 60 330 230 Measured Tg [° C.] with DSC 2561 24 2 (midpoint) Acid value theoretical on 15.6 14.8 0 15.6 solids [mgKOH/g].Preparation of a Blend of Oligomer Dispersion DA1 and Dispersed PolymerP1=A1P1

A 500 cm³ flask, equipped with a stirrer, was loaded with DA1 (150.0 g)in a nitrogen atmosphere, after which dispersion P1 (89.24 g) was addedwhile stirring the mixture. The blend was stirred for an additional 20minutes at room temperature. The blend had a solids content of 38.2 wt%, and a pH of 7.5.

A range of blends from oligomer dispersions A1 to A6 and dispersedpolymers P1 to P4 was prepared according to similar procedures using thecomponents given in Table 3 below. The blends for comparative examplesC1 and C2 (with too much oligomer or dispersed polymer) are also givenin Table 3 below.

TABLE 3 Components (g) A1P1 A1P2 A2P3 A3P1 A1A4P1 Oligomer dispersion 1DA1 DA1 DA2 DA3 DA1 Oligomer dispersion 1(g) 150.00 100.00 100.00 68.8971.43 (% of total solids) 50 40 35 30 25 Oligomer dispersion 2 — — — —DA4 Oligomer dispersion 2(g) — — — — 28.57 (% of total solids) — — — —10 Dispersed polymer P1 P2 P3 P1 P1 Dispersed polymer (g) 89.24 129.60111.43 94.08 107.14 (% of total solids) 50 60 65 70 65 Blend solids (%)38.2 32.9 40.5 53.7 41.4 C1- C2- Components (g) A1A4P1* A1A54 A6P1 A1P2A1P1 Oligomer dispersion 1 DA1 DA1 DA6 DA1 DA1 Oligomer dispersion 1(g)71.43 71.43 50.00 10.00 180.0 (% of total solids) 25 25 25 5 95 Oligomerdispersion 2 DA4 DA5 — — — Oligomer dispersion 2(g) 28.57 28.57 — — — (%of total solids) 10 10 — — — Dispersed polymer P1 P4 P1 P2 P1 Dispersedpolymer (g) 107.14 123.81 86.54 163.94 5.51 (% of total solids) 65 65 7595 5 Additive Iron oxide — — — — paste (48%) Additive (g) 8.29 — — — —Blend solids (%) 41.7 38.3 43.9 46.7 30.9Pigmented Paint Composition Comprising A1P1

A 500 cm³ flask, equipped with a stirrer, was loaded with A1P1 (200.0 g)and a TiO₂-based pigment paste (94.78 g; 70.8 wt % titanium dioxide) ina nitrogen atmosphere, and the mixture was stirred for 30 minutes atambient temperature. The resulting paint formulation had a solidscontent of 50.2%. Then a wetting agent (Byk 24, 0.2 g) was addedfollowed by a thickener (Borchigel L75N/H₂O: 1/1, available from Bayer)until a viscosity of 4000 to 6000 mPa·s was reached. The paintformulation was left undisturbed for 24 h, then stirred up to mix thecontents intimately, checked (and when necessary corrected) for itsviscosity. The drying results are given in Table 4 below.

Paint examples 2 to 8 (and the comparative examples C1 and C2) wereprepared according to similar procedures using the components given inTable 4. A1A4P1* is a non pigmented example. The function of the ironoxide paste [1.9% wt % iron oxide of total blend] is to add a tint tothe otherwise clear composition to aid the open and wet edge timeassessments. In the pigmented examples around 22 wt % of titaniumdioxide is added to the blend. The drying and other properties of theseexamples are also given in Table 4.

The equilibrium viscosities of the paint examples 1 to 8 (and thecomparative examples C1 and C2) are given in Tables 5.1 to 5.10.

TABLE 4 Paint Example 1 2 3 4 5 Blend A1P1 A1P2 A2P3 A3P1 A1A4P1 Blend(g) 200.00 229.60 211.43 163.97 207.14 Pigment paste (g) 94.78 93.00105.41 86.03 105.51 Open Time (mins) 37 65 23 50 55 Wet edge time 21 3515 26 35 (mins) Tack-free time (hrs) 8–17 <0.5 <0.5 0.75–1   0.75–1  Dust-free time (hrs) 2 3–3.5 9–16 7–8 20 Thumb-hard time 9–24 4.5 9–24 921–24 (hrs) Sandability (hrs) 9–24 9–16  9–24  9–24 28–30 König Hardness— 76 56 14 — (Seconds) Water resistance 4 5 3–4  3–4 — Paint Example 6 78 C1 C2 Blend A1A4P1* A1A5P4 A6P1 C1- C2- A1P2 A1P1 Blend (g) 215.43223.81 136.54 200.00 185.51 Pigment paste (g) 0.0 105.51 73.86 127.0470.53 Open Time (mins) 50 65 57 17 70 Wet edge time 24 32 30 5 26 (mins)Tack-free time (hrs) 0.75–1   0.5 0.5 <0.5 3–4 Dust-free time (hrs)20–21   2–2.5  9–16 3–4 >140 Thumb-hard time 24 8 25–26 7–8 >140 (hrs)Sandability (hrs) 30  9–24 24–48  9–24 >140 König Hardness 10 33 24 91 —(Seconds) Water resistance — 5 3–4 4–5 2–3 Key: — = not measured Due tothe time taken for some of these tests, some of the coatings were leftovernight without continuous testing. Therefore when the data says 9–20it means that by 9 hours it was not sandable but that by 24 hours it wassandable.

TABLE 5.1 Equilibrium viscosity of example 1. Shear rate Shear rateShear rate Shear rate 0.1 s⁻¹ 1.0 s⁻¹ 10.0 s⁻¹ 77.9 s⁻¹ Calculatedviscosity viscosity viscosity viscosity Time (min) Solids (%) (Pa · s)(Pa · s) (Pa · s) (Pa · s) 0.0 50.20 9 6 4  3 6.5 58.35 22 13 9  7 13.570.18 32 23 15 10 20.0 79.00 43 31 21 12 26.0 83.31 241 138 87 13 31.587.49 799 335 162 21 37.0 90.90 3978 688 210 — 40.0 91.68 5382 833 228 —

TABLE 5.2 Equilibrium viscosity of example 2. Shear rate Shear rateShear rate Shear rate 0.1 s⁻¹ 1.0 s⁻¹ 10.0 s⁻¹ 77.9 s⁻¹ Calculatedviscosity viscosity viscosity viscosity Time (min) Solids (%) (Pa · s)(Pa · s) (Pa · s) (Pa · s) 0 45.0 7 2 1 0.5 3 48.7 17 9 4 2 8 57.1 789127 28 10 13 64.4 23530 7311 446 9 18 70.6 57550 17560 3421 510 25 77.3113800 40260 6048 —

TABLE 5.3 Equilibrium viscosity of example 3. Shear rate Shear rateShear rate Shear rate 0.1 s⁻¹ 1.0 s⁻¹ 10.0 s⁻¹ 77.9 s⁻¹ Calculatedviscosity viscosity viscosity viscosity Time (min) Solids (%) (Pa · s)(Pa · s) (Pa · s) (Pa · s) 0 51.9 331 68 14 4 4 57.9 1062 202 37 8 762.8 1676 429 119 18 14 72.4 43350 13950 2236 58 17 75.8 116900 8507029810 — 27 83.5 152000 116800 101400 —

TABLE 5.4 Equilibrium viscosity of example 4. Shear rate Shear rateShear rate Shear rate 0.1 s⁻¹ 1.0 s⁻¹ 10.0 s⁻¹ 77.9 s⁻¹ Calculatedviscosity viscosity viscosity viscosity Time (min) Solids (%) (Pa · s)(Pa · s) (Pa · s) (Pa · s) 0 53.7 8 4 3 1 3 56.7 32 15 9 3 7 62.8 154 7439 11 13 71.9 5375 1306 172 23 17 77.8 20660 8787 1732 677 23 86.6901500 205700 8181 712 29 95.3 1103000 232100 11300 1163

TABLE 5.5 Equilibrium viscosity of example 5. Shear rate Shear rateShear rate Shear rate 0.1 s⁻¹ 1.0 s⁻¹ 10.0 s⁻¹ 77.9 s⁻¹ Calculatedviscosity viscosity viscosity viscosity Time (min) Solids (%) (Pa · s)(Pa · s) (Pa · s) (Pa · s) 0 52.7 13 2 1 0.3 4 56.4 30 5 2 1 7 60.5 8617 5 3 14 69.2 1388 403 113 18 17 72.7 27080 5326 645 200 24 80.3 20900030360 2854 249 28 84.2 220700 32670 4369 454

TABLE 5.6 Equilibrium viscosity of non-pigmented example 6. Shear rateShear rate Shear rate Shear rate 0.1 s⁻¹ 1.0 s⁻¹ 10.0 s⁻¹ 77.9 s⁻¹Calculated viscosity viscosity viscosity viscosity Time (min) Solids (%)(Pa · s) (Pa · s) (Pa · s) (Pa · s) 0 41.7 21 5 2 1 3 45.6 58 13 6 4 752.3 253 66 29 18 12 60.7 5753 1151 261 86 16 67.3 169400 27070 45631297 22 77.3 229500 45190 7512 1993

TABLE 5.7 Equilibrium viscosity of example 7. Shear rate Shear rateShear rate Shear rate 0.1 s⁻¹ 1.0 s⁻¹ 10.0 s⁻¹ 77.9 s⁻¹ Calculatedviscosity viscosity viscosity viscosity Time (min) Solids (%) (Pa · s)(Pa · s) (Pa · s) (Pa · s) 0 50.0 23 4 1 0.3 3 52.8 57 9 2 0.7 7 57.1152 24 6 2 13 63.6 610 105 26 13 17 68.0 9782 1581 230 87 24 75.9 4608013390 4559 — 29 81.6 1302000 179600 — —

TABLE 5.8 Equilibrium viscosity of example 8. Shear rate Shear rateShear rate Shear rate 0.1 s⁻¹ 1.0 s⁻¹ 10.0 s⁻¹ 77.9 s⁻¹ Calculatedviscosity viscosity viscosity viscosity Time (min) Solids (%) (Pa · s)(Pa · s) (Pa · s) (Pa · s) 0 54.8 18 4 1 1 4 59.9 60 14 5 3 8 65.9 34966 21 11 14 74.4 120300 29010 6885 76 17 78.4 216800 42400 8226 638 2385.9 439700 85180 15610 1892

TABLE 5.9 Equilibrium viscosity of comparative example C1. Shear rateShear rate Shear rate Shear rate 0.1 S⁻¹ 1.0 s⁻¹ 10.0 s⁻¹ 77.9 s⁻¹Calculated viscosity viscosity viscosity viscosity Time (min) Solids (%)(Pa · s) (Pa · s) (Pa · s) (Pa · s) 0 46.7 6 4 3 2 3 49.1 25 15 8 4 1652.3 907 289 66 19 11 56.6 14300 5932 3693 851 17 61.0 386400 123400232600 —

TABLE 5.10 Equilibrium viscosity of comparative example C2. Shear rateShear rate Shear rate Shear rate 0.1 s⁻¹ 1.0 s⁻¹ 10.0 s⁻¹ 77.9 s⁻¹Calculated viscosity viscosity viscosity viscosity Time (min) Solids (%)(Pa · s) (Pa · s) (Pa · s) (Pa · s) 0 43.0 2 2 1 1 4 48.1 9 9 8 7 8 53.937 29 25 22 15 62.5 210 55 24 18 23 69.9 1467 216 51 27 26 72.0 2295 34397 57 30 74.3 2409 446 151 93 37 76.7 2513 465 157 97 41 77.2 2576 488174 113 48 76.5 2395 472 182 118

1. An aqueous coating composition comprising: a) 1 to 64 wt % of anon-crosslinkable water-dispersible oligomer(s); b) 4 to 76 wt % of adispersed polymer(s); c) 0 to 20 wt % of co-solvent; d) 20 to 80 wt % ofwater; where a)+b)+c)+d)=100%; where the weight ratio of a):b) is in therange of from 8:92 to 80:20; and wherein said composition when drying toform a coating has the following properties: i) an open time of at least20 minutes; ii) a wet edge time of at least 10 minutes; iii) a tack-freetime of ≦24 hours; iv) an equilibrium viscosity of ≦5,000 Pa·s, at anysolids content when drying in the range of from 20 to 55% by weight ofthe composition, using any shear rate in the range of from 9±0.5 to 90±5s⁻¹ and at 23±2° C.
 2. An aqueous coating composition according to claim1 wherein said non-crosslinkable oligomer(s) has a solution viscosity≦150 Pa·s, as determined from a 80% by weight solids solution of thenon-crosslinkable oligomer(s) in at least one of the solvents selectedfrom the group consisting of N-methylpyrrolidone, n-butylglycol andmixtures thereof, using a shear rate of 90±5 s⁻¹ and at 50±2° C.
 3. Anaqueous coating composition according to claim 1 wherein saidnon-crosslinkable oligomer(s) has a solution viscosity ≦250 Pa·s, asdetermined from a 70% by weight solids solution of the non-crosslinkableoligomer(s) in a solvent mixture consisting of: i) at least one of thesolvents selected from the group consisting of N-methylpyrrolidone,n-butylglycol and mixtures thereof; ii) water and iii)N,N-dimethylethanolamine; where i), ii) and iii) are in weight ratios of20/7/3 respectively, using a shear rate of 90±5 s⁻¹ and at 23±2° C. 4.An aqueous composition according to claim 1 wherein saidnon-crosslinkable oligomer(s) is selected from the group comprisingpolyurethane oligomer(s), vinyl oligomer(s), polyamide oligomer(s),polyether oligomer(s), polysiloxane oligomer(s), polyester oligomer(s),hyperbranched oligomer(s) and mixtures thereof.
 5. An aqueouscomposition according to claim 1 wherein said composition has anequilibrium viscosity ≦5,000 Pa·s when measured using any shear rate inthe range of from 0.09±0.005 to 90±5 s⁻¹, and an equilibrium viscosityof ≦3,000 Pa·s when measured using any shear rate in the range of from0.9±0.05 to 90 ±5 s⁻¹, and an equilibrium viscosity of ≦1,500 Pa·s whenmeasured using any shear rate in the range of from 9±0.5 to 90±5 s¹, atany solids content when drying in the range of from 20 to 55% by weightof the composition and at 23±2° C.
 6. An aqueous composition accordingto claim 1 wherein the non-crosslinkable oligomer(s) has a measuredweight average molecular weight in the range of from 1,000 to 80,000Daltons.
 7. An aqueous composition according to claim 1 wherein thenon-crosslinkable oligomer(s) has a PDi ≦15.
 8. An aqueous compositionaccording to claim 1 wherein the non-crosslinkable oligomer(s) has ameasured Tg in the range of from −120 to 250° C.
 9. An aqueouscomposition according to claim 1 wherein the dispersed polymer(s) has ameasured weight average molecular weight ≧90,000 Daltons.
 10. An aqueouscomposition according to claim 1 wherein the dispersed polymer(s) has ameasured weight average molecular weight <90,000 Daltons with theproviso that the dispersed polymer(s) has a solution viscosity >150Pa·s, as determined from a 80% by weight solids solution of thedispersed polymer(s) in at least one of the solvents selected from thegroup consisting of N-methylpyrrolidone, n-butylglycol and mixturesthereof, using a shear rate of 90±5 s⁻¹ and at 50±2° C.
 11. An aqueouscomposition according to claim 1 wherein the dispersed polymer(s) hasparticle size in the range of from 25 to 1000 nm.
 12. An aqueouscomposition according to claim 1 wherein the dispersed polymer(s) has anacid value below 150 mgKOH/g.
 13. An aqueous composition according toclaim 1 wherein the dispersed polymer(s) has a measured Tg in the rangeof from −50 to 300° C.
 14. An aqueous composition according to claim 1wherein the dispersed polymer(s) is a vinyl polymer.
 15. An aqueouscoating composition according to claim 1 additionally comprising apigment.
 16. A coating obtained from the aqueous composition accordingto claim 1.